Home DIY and flat-pack
You need 4 mm and 5 mm, a holder, and both size systems if the house mixes metric furniture with older imperial fittings. The MULWARK folding set keeps metric sizes to 8 mm and SAE sizes to 1/4 in in one body.
Allen key comparison 2026
The best Allen keys, compared.
Top pick: MULWARK folding metric and SAE set – Highest score in this set, with 4.7 from 5,474 reviews and both size systems in one folding body. Best value: Stanley 2-69-264 folding set – Highest value score among the rest, at about £7.42, with 4.5 from 4,149 reviews and a metric span to 8 mm. Updated October 2026.
An Allen key is a hexagon socket screw key. It may be an L-shape, a folding set, a ring of short keys or a T-handle, and the working end fits an internal hex. In the UK the everyday name is Allen key. Hex key means the same tool, and the standards name is hexagon socket screw key under ISO 2936:2014. You buy one for bikes, flat-pack furniture, machinery and the odd imperial fastener left in an older fitting. A suitable key is the size that seats fully, without wobble. Use the straight end for the tight turn. A ball end is only for turning at an angle once the bolt is already moving. Metric and imperial sizes that are close will start in the wrong socket and round the hex. UK bikes are metric. A mixed house needs both systems, labelled. A useful metric spread is 1.5, 2, 2.5, 3, 4, 5, 6, 8 and 10 mm. How the two size systems differ is set out in the [metric or imperial Allen key guide](/hub/hand-tools/allen-key/sub/allen-key-metric-or-imperial).
An Allen key is a hexagon socket screw key. It may be an L-shape, a folding set, a ring of short keys or a T-handle, and the working end fits an internal hex. In the UK the everyday name is Allen key.
32 products checked · 58 hrs invested · +21,400 readers
9 of 9: Best Allen keys compared
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1-2 of 9Best overall
Best value
9.0/10
7.6/10
6.0/10
5.3/10
6.2/10
7.8/10
7.1/10
6.4/10
7.1/10
∼ £15
∼ £9
∼ £13
∼ £40
∼ £20
∼ £7
∼ £10
∼ £4
∼ £4
4.7(5,474)
4.7(349)
4.7(121)
4.7(5)
4.6(79)
4.5(4,149)
4.5(1,203)
4.2(544)
4.1(2,775)
Personal buying guide
Which Allen key fits you?
Question 1 of 2
Which fasteners are you turning?
The best Allen keys in detail
Our view
The MULWARK folding set lists eight metric sizes from 1.5 mm to 8 mm and nine SAE sizes from 5/64 in to 1/4 in, with a grip, at about £14.99. Across 5,474 amazon.co.uk reviews the line is 4.7, the largest sample in this comparison, which is why it is the top pick here. Buyers who are describing this folding hex tool like that the keys stay in one body, that the grip adds leverage over a bare key, and that metric and SAE sit together for occasional home jobs. One buyer says the keys do not lock out, and another says there is no bend, so a tight corner is awkward. Several of the first 50 reviews describe Torx bits, a three-tool set or a ball end that the bullets do not name, so you should match the parcel to the size list rather than to those comments. The title says 17 pieces and also 2 pack, and the unit count is 2, which leaves the pack quantity unclear. No repeated snapped-key report appears in the reviews that match this listing.
Pros
- 4.7 from 5,474 amazon.co.uk reviews, the largest sample here
- Metric to 8 mm and SAE to 1/4 in in one folding body
- Grip described as more leverage than a bare key
- Keys stay together, which buyers prefer to a loose ring
- about £14.99, with no repeated snapped key in the matching reviews
Cons
- Title says 17 pieces and also 2 pack
- Some of the first 50 reviews describe tools the bullets do not list
- One buyer says the keys do not lock, and one says there is no bend
- Metric list stops at 8 mm, so there is no 10 mm key
Best for: You want one folding tool with metric and SAE sizes for occasional home jobs, and you will check that the parcel matches the hex size list.
Less suitable: You need a 10 mm key, a locked arm, or a long L-key that reaches a recessed bolt.
Specifications
- Model
- MULWARK folding metric and SAE set
- Brand
- MULWARK
- Price
- ∼£15
- Customer rating
- 4.7/5(5,474)
- Tip
- Hex end
- Sizes
- 1.5–8 mm; 5/64–1/4 in
- Size system
- Metric and SAE
- Pieces
- 17; pack unclear
- Storage
- Folding body
- Steel
- Alloy steel
- Grip
- Ergonomic handle
Common questions
Is this one folding tool or a 2-pack?
The title says 17 pieces and 2 pack. Unit count and number of packs are both 2. The size list is 8 metric keys plus 9 SAE keys.
Does it include a case?
The bullets do not name a case. Included components say a folding Allen wrench set.
Are Torx bits included?
The listing names hex ends only. Some of the first 50 reviews describe Torx bits that are not in the bullets.
Our view
The AMTOVL 9-piece set is nine colour-coded metric L-keys from 1.5 mm to 10 mm, listed at about £9.49. Across 349 amazon.co.uk reviews the line is 4.7, and buyers who name a job use the long arm on bikes, children's bikes, flat-pack and a recessed grub screw. Colour sleeves are what people mention when two of you are working or the light is poor, and a clip or holder is what they say keeps the keys from vanishing in a toolbox. The included-components line does not name a case, so that holder is a review report rather than a stated part. The title and head style say a hex end, while one bullet calls the same set a ball-end set, and the size-system field says SAE even though no imperial size is printed. One buyer said the set was too small for the job. In the 50 reviews read there is no repeated report of a bent or rounded tip.
Pros
- 4.7 from 349 amazon.co.uk reviews at about £9.49
- Metric 1.5–10 mm, including 8 mm and 10 mm
- Colour coding praised for finding the size in poor light
- Long arm used on bikes, flat-pack and a recessed grub screw
- No repeated bent or rounded tip in the 50 reviews read
Cons
- Title says hex end and one bullet says ball end
- Size-system field says SAE with no imperial sizes printed
- A case is not on the included-components line
- One buyer said the set was too small for the job
Best for: You want colour-coded metric L-keys from 1.5 mm to 10 mm for bikes and flat-pack, and you can check the tip in the parcel.
Less suitable: You need a printed imperial list, a ball end the title actually names, or a case stated in the included line.
Specifications
- Model
- AMTOVL 9-piece metric set
- Brand
- AMTOVL
- Price
- ∼£9
- Customer rating
- 4.7/5(349)
- Tip
- Hex; ball claimed
- Sizes
- 1.5–10 mm
- Size system
- Metric; SAE unlisted
- Pieces
- 9
- Storage
- Not on included line
- Colour coding
- Yes
- Steel
- Chrome vanadium
- Grip
- Textured
Common questions
Does this AMTOVL set include a case?
The included-components line does not name a case. Reviews mention a holder or clip that keeps the keys together.
Are the keys heat-treated?
The bullets say every key is heat-treated, chrome-plated and colour-coded.
Is the tip a ball end?
The title and head style say metric hex end. One bullet calls the same set a ball-end set.
Our view
The ELEAD UK-70010 is a 31-piece set at about £12.99: 15 long keys, 15 short keys and a torque handle in a carrying case, with inch and metric claimed and no individual sizes printed. It scores 4.7 from 121 amazon.co.uk reviews. Reviewers who are pleased with it like having long and short keys of both systems in one case, and they say the handle adds grip, including for weaker hands. The repeated complaint is soft metal: flex, rounded tips and deformed ends after a few uses, with small keys compared by one buyer to paperclips. The plastic handle breaks in some accounts and was missing in one, and one case zip would not close again after it had been fully opened. A review mentions a ball head and colour coding that the bullets do not state. Bikes are asked on the page and are not named in the bullets, so you cannot check a bike size list before the set arrives.
Pros
- 4.7 from 121 amazon.co.uk reviews at about £12.99
- Long and short keys plus a torque handle in a case
- Inch and metric both claimed
- Handle liked for grip when it is present and intact
Cons
- Exact sizes are not printed
- Tips described as soft, rounded or bent after a few uses
- Torque handle snaps or can arrive missing
- One zip would not close again after it was fully opened
Best for: You want long and short keys of both systems in a case, and you will test the tips on a non-critical bolt first.
Less suitable: You need the size list before you pay, or keys that reviews describe as holding their shape.
Specifications
- Model
- ELEAD 31-piece hex key set
- Brand
- ELEAD
- Price
- ∼£13
- Customer rating
- 4.7/5(121)
- Tip
- Hex
- Sizes
- Sizes not listed
- Size system
- Metric and SAE
- Pieces
- 31
- Storage
- Carrying case
- Steel
- Chrome vanadium
- Grip
- Torque handle
Common questions
Does the ELEAD set include a case and a handle?
The bullets name a carrying case and a torque handle, with 15 long keys and 15 short keys.
Are the exact metric and inch sizes printed?
No. The listing says inch and metric coverage and does not list each size.
Are the keys heat-treated?
The bullets say heat-treated steel with a black-oxide finish. Reviews often say the metal is soft and the tips round.
Our view
The AMTOVL T-handle set is ten metric sliding handles from 2 mm to 10 mm, with engraved aluminium sleeves and a carry box, at about £39.89. It scores 4.7 from only five amazon.co.uk reviews, and only four review texts are in the file, two of them outside the UK, so the stars are not a large British sample. The UK comments that are there like the T-handle for leverage, the 2–10 mm span for home, garage and bike jobs, and the long shafts for recessed fasteners. One UK review calls the case adequate rather than the toughest, and warns that driving from the short end puts a lot of force through the long shaft. There is no 1.5 mm key. No broken key or failed detent shows up in those four texts, which is too little evidence to treat the sliding collar as proven. At this price you are paying for the handle, and a plain L-key set covers the same millimetres for much less if you do not need the T.
Pros
- Sliding T-handle from 2 mm to 10 mm, with a carry box
- Long shafts for recessed fasteners, in the few UK comments
- Sizes engraved on the sleeves
- Chrome vanadium named, with aluminium sleeves
Cons
- about £39.89 with only five amazon.co.uk reviews
- Two of the four review texts are not UK reviews
- No 1.5 mm key
- Short end can overload the long shaft, in one UK review
Best for: You specifically want a sliding T-handle for leverage on 2–10 mm metric fasteners and you accept a thin review file.
Less suitable: You need 1.5 mm, a large UK sample, or the same sizes at an L-key price.
Specifications
- Model
- AMTOVL 10-piece T-handle set
- Brand
- AMTOVL
- Price
- ∼£40
- Customer rating
- 4.7/5(5)
- Tip
- Hex
- Sizes
- 2–10 mm
- Size system
- Metric
- Pieces
- 10
- Storage
- Carry box
- Colour coding
- No
- Steel
- Chrome vanadium
- Grip
- Sliding T-handle
Common questions
Can each key switch between L and T?
The bullets say a sliding 3-way design moves between L-shaped and T-shaped, with a free-spinning collar.
Does the set include 1.5 mm for small bike bolts?
No. Included sizes start at 2 mm and run to 10 mm.
Is the carry box part of the set?
Yes. Included components list one carry box and the ten wrenches. A UK review calls the case adequate rather than the toughest.
Our view
The YOIbuy PRO set is nine metric keys from 1.5 mm to 10 mm with a ball end and a straight hex end, at about £19.90. It scores 4.6 from 79 amazon.co.uk reviews, a smaller sample than the high-volume folding sets on this page. Reviewers who name a job use the long arm on bikes, cars, furniture and machinery, and several accept the bullet claim of about 25 degrees on the ball end. Colour sleeves are compared with dearer colour-coded sets, and the SK2 tips are described as a close fit that did not twist in those reviews. The repeated complaint is the plastic holder: keys are hard to pull out, and one buyer nearly reached for pliers, while another found the organiser loose. A reviewer warns they are not stainless and can rust if you put them away dry. A Japanese review says the ball-end clip starts at 4 mm, so the smallest keys may not be the angled end.
Pros
- Metric 1.5–10 mm with a ball end and a hex end
- 4.6 from 79 amazon.co.uk reviews
- Ball end accepted at about 25 degrees in the reviews that mention the angle
- SK2 tips described as a close fit on tight bolts
- Colour coding compared with dearer colour-coded sets
Cons
- Holder often too tight to pull a key out
- about £19.90, and only 79 reviews
- Not stainless; one reviewer warns of rust if left dry
- Ball-end clip may not be on the smallest keys
Best for: You want a metric long-arm set with a ball end for angled access on bikes, cars or furniture, and you will check the holder before you rely on it.
Less suitable: You want keys that slide straight out of the holder, or a large UK review sample at a lower price.
Specifications
- Model
- YOIbuy PRO 9-piece ball-end set
- Brand
- YOIbuy PRO
- Price
- ∼£20
- Customer rating
- 4.6/5(79)
- Tip
- Ball and hex
- Sizes
- 1.5–10 mm
- Size system
- Metric
- Pieces
- 9
- Storage
- Plastic holder
- Colour coding
- Yes
- Steel
- SK2
- Grip
- Colour sleeves
Common questions
Do the ball ends work at an angle?
The bullets say the ball end allows angled access up to 25 degrees. Reviews that mention the angle accept that claim. That angle is a maker figure, not a high-torque rating.
Are the keys easy to take out of the holder?
The listing does not claim easy removal. Several reviews say the holder grips the keys tightly.
Will this set cover a bike?
The bullets name bicycles among the uses, with metric sizes from 1.5 mm to 10 mm.
Our view
The Stanley 2-69-264 is an eight-piece metric folding set, 1.5–8 mm on the included-components line, at about £7.42, and it is the best value pick on this page. Across 4,149 amazon.co.uk reviews the line is 4.5, the second-largest sample here, and the listing ranks it 1 in Hex Keys. Reviewers use it on bikes, a bed, a dining chair and a uPVC door, and they like that the folding body keeps the sizes together in a car or a bike bag. The repeated limit is that the keys do not lock, so unused arms flip open and snag, and the plastic sides flex when you apply force, which caps the torque. The black phosphate finish can come off on your hands, one set was slightly rusty on opening, and one buyer returned it as flimsy next to a Stanley FatMax set. The material row says Karton, which reads as packaging rather than a steel grade, and the individual sizes are not listed beyond the 1.5–8 mm span. It is a pocket set for light metric jobs, and it is the wrong tool when you need a key to stay at 90 degrees in a tight spot.
Pros
- about £7.42 for a Stanley folding set, 4.5 from 4,149 reviews
- Metric 1.5–8 mm in a pocket body
- Used on bikes, flat-pack and a door alignment
- Keeps sizes together better than a loose ring, in the reviews
- Listed as 1 in Hex Keys
Cons
- Arms do not lock and flip open in a toolbox
- Plastic sides flex under load, which limits torque
- No 10 mm key, and individual sizes are not listed
- Finish can mark hands; one light rust report on opening
Best for: You want a named metric folder for a car, a bike bag or light flat-pack, and you do not need 10 mm.
Less suitable: You need a locked arm, high torque, or a 10 mm key.
Specifications
- Model
- Stanley 2-69-264 folding set
- Brand
- Stanley
- Price
- ∼£7
- Customer rating
- 4.5/5(4,149)
- Tip
- Hex, chamfered
- Sizes
- 1.5–8 mm
- Size system
- Metric
- Pieces
- 8
- Storage
- Folding handle
- Colour coding
- No
- Grip
- Over-moulded
Common questions
Which metric sizes are in the Stanley set?
Included components say an 8-piece folding set, 1.5–8 mm. The listing does not print each size.
What are the keys made of?
The material row says Karton. The finish is black phosphate. A steel grade is not given.
Do the arms lock when folded?
The listing does not claim a lock. Reviews often say unused keys flip open and the plastic sides flex under load.
Our view
The LOZAGU set is 35 pieces at about £9.99: 15 SAE keys from 0.028 in to 3/8 in, 17 metric keys from 0.7 mm to 10 mm, two L-shaped screwdrivers and a torque handle, in a box with size slots. It scores 4.5 from 1,203 amazon.co.uk reviews. Reviewers use it on furniture, a wheelchair and 3D printers, and they often call the box useful for keeping that wide range in order. The keys themselves are described as strong for the price when the plastic handle is left out of the job. The repeated failure is that handle: several buyers say it snapped or felt flimsy on first use. The box catch can be stiff, keys can be fiddly to clip back, and one buyer returned the set because keys fell out of the clips. Bicycles are asked on the page and are not named in the bullets.
Pros
- Printed SAE list to 3/8 in and metric list to 10 mm
- 4.5 from 1,203 amazon.co.uk reviews at about £9.99
- Box with size slots often called useful
- Keys described as strong when the handle is not the lever
Cons
- Plastic torque handle snaps or feels flimsy, including on first use
- Box catch can be stiff and clips can drop keys
- Bicycles are not named in the bullets
- Smaller keys feel cheap to at least one buyer
Best for: You want a boxed metric and SAE spread, including very small keys and 3/8 in, and you will tighten with the L-key rather than the plastic handle.
Less suitable: You are buying it for the torque handle, or you need a listing that names bicycles.
Specifications
- Model
- LOZAGU 35-piece hex key set
- Brand
- LOZAGU
- Price
- ∼£10
- Customer rating
- 4.5/5(1,203)
- Tip
- Hex, chamfered
- Sizes
- 0.7–10 mm; to 3/8 in
- Size system
- Metric and SAE
- Pieces
- 35
- Storage
- Size-slot box
- Steel
- Chrome vanadium
- Grip
- Torque handle
Common questions
Does it come with a storage box?
Yes. The bullets describe a box with a slot and a size mark for each wrench.
What else is in the 35 pieces?
The bullets count 15 SAE keys, 17 metric keys, one torque handle and two L-shaped screwdrivers (PH1 SL3/16 and PH2 SL1/4).
Do reviews say the torque handle lasts?
Several reviews say the plastic handle snapped or felt flimsy on first use. The keys themselves are more often praised.
Our view
The D.A.Y. Republic set is 14 hex keys on a metal ring at about £3.98, made in China, and the listing weight is 120 g. Across 544 amazon.co.uk reviews the line is 4.2. The bullets say metric sizes from 2 mm to 8 mm plus imperial options, and they name 2 mm, 2.5 mm and 3 mm as examples, but they do not print the full size list. Buyers who like it treat it as a one-off for furniture, a window lock or a toilet holder. One review likes a split ring that can hang on a nail, and colour coding of metric against imperial, which the listing itself does not state. The repeated failure is the ring, the springs or the clips: keys fall off, sometimes on opening, and they do not lie straight. Some keys bend, lose shape or break under little force, and single reviews mention a poor fit, rust on arrival, or keys that were dirty and sticky.
Pros
- about £3.98, with 4.2 from 544 amazon.co.uk reviews
- Metric range stated from 2 mm to 8 mm
- Fine for a light furniture or lock job in some reviews
- Carbon steel named, at 120 g
Cons
- Keys fall off the ring, springs or clips
- Some keys bend, deform or snap under little force
- Full imperial list is not printed
- Odd reports of rust, dirt or a poor fit on arrival
Best for: You want a spare ring of small keys for a light, one-off job and the missing size list is acceptable.
Less suitable: You need every size printed before you buy, or a ring that keeps the keys on.
Specifications
- Model
- D.A.Y. Republic 14-piece ring set
- Brand
- D.A.Y. Republic
- Price
- ∼£4
- Customer rating
- 4.2/5(544)
- Tip
- Hex
- Sizes
- 2–8 mm; imperial unlisted
- Size system
- Metric and SAE
- Pieces
- 14
- Storage
- Metal ring
- Steel
- Carbon steel
Common questions
Does this set include a case?
No. Included components name the hexagonal key set. Storage on the listing is the metal ring.
Which sizes are listed?
The bullets say metric from 2 mm to 8 mm plus imperial options, and they name 2 mm, 2.5 mm and 3 mm as examples. A full size list is not printed.
Do the keys stay on the ring?
The bullets say the ring keeps them together. Reviews repeatedly say the ring or springs are flimsy and keys fall off.
Our view
The G4GADGET set is 14 L-keys on a metal ring at about £3.99, with metric sizes from 1.5 mm to 6 mm and imperial sizes from 1/16 in to 7/32 in. Across 2,775 amazon.co.uk reviews the line is 4.1, so the sample is large and the stars are the lowest in this comparison. Buyers who are content with it use it for light work such as furniture, a bunk bed, curtain poles, a guitar or a dog guard, when they do not yet know which small size they need. The dominant complaint is that keys jump off the ring or the spring clips, sometimes as soon as the pack is opened, and some say a key taken off for the long arm will not clip back. Tips are often called soft or brittle: they warp, wear or lose their shape when a bolt is tightened. The bullets say hardened alloy steel and the material row says carbon steel, so the hardness claim and the reviews do not match. There is no 8 mm or 10 mm key on the printed list.
Pros
- about £3.99 for metric 1.5–6 mm and imperial 1/16–7/32 in
- 4.1 from 2,775 amazon.co.uk reviews
- Useful for light furniture jobs when the size is unknown
- Both size systems are printed
Cons
- Keys fall off the ring or the clips, often on opening
- Tips described as soft, warped or worn through
- Long arm means taking the key off the ring
- No 8 mm or 10 mm key, and the steel lines disagree
Best for: You want a cheap mixed ring for a light, one-off furniture job and you can afford to lose a key.
Less suitable: You need 8 mm or 10 mm, or a set that stays on its holder when you carry it.
Specifications
- Model
- G4GADGET 14-piece ring set
- Brand
- G4GADGET
- Price
- ∼£4
- Customer rating
- 4.1/5(2,775)
- Tip
- Hex
- Sizes
- 1.5–6 mm; 1/16–7/32 in
- Size system
- Metric and imperial
- Pieces
- 14
- Storage
- Metal ring
- Steel
- Disputed grade
Common questions
Does the ring keep the keys together?
The bullets say a detachable metal ring stops keys going missing. In the reviews, keys often fall off the ring or the clips.
Can you use the long arm while it is on the ring?
Reviews say you use the short end on the ring, and taking the key off for the long end can stop it clipping back on.
Is the steel as hard as the bullets claim?
The bullets say hardened alloy steel. The material row says carbon steel. Reviews often describe soft or brittle tips.
How we compared
For this comparison we scored nine Allen key listings on amazon.co.uk. Prices, stars and review counts are the figures on those listings on 22 October 2026. There was no workshop test. Stars count for 40, the size of the review sample for 20, the use notes in the file for 25, and value in this set for 15.
1
Stars
40%The amazon.co.uk rating, divided by 5 and multiplied by 40. A missing rating line would score 0. This is the published star line, not a lab score.
2
Review sample
20%Larger amazon.co.uk review counts score more, from 2 points under 20 reviews up to 20 points at 2,000 reviews or more. A thin sample cannot carry the same weight as several thousand reviews.
3
Use in the file
25%Review notes that name a real job score higher when they do not describe keys leaving the ring, tips rounding or bending, or a handle that snaps or flexes under load. A listing line that contradicts the tip, the piece count, the sizes or the material is marked down once.
4
Value in this set
15%Lower shelf prices score more. Both size systems printed, a metric span to at least 6 mm, a named holder, and 100 or more reviews add points. Repeated lost keys, rounded tips or a snapped handle are marked down once. The highest score is the top pick and is not also best value.
Independent review
Last updated: October 2026
8 sources checked
Allen key buying guide
An Allen key is the tool for an internal hex. Match the size system first, then the sizes you will actually meet, then the end and the holder. A piece count that includes a plastic handle is not a count of hex sizes.
What is an Allen key?
An Allen key is a hexagon socket screw key. The working end is a six-sided tip that fits an internal hex in a bolt or a grub screw. In the UK the everyday name is Allen key. Hex key means the same thing. The standards name, under ISO 2936:2014, is hexagon socket screw key. That edition, confirmed in 2025, sets dimensions, a proof-torque test, marking and a minimum hardness for keys used on socket screws up to property class 12.9. The sample drawing is a straight hex, not a ball.
Best for
- Home DIY and flat-pack, where 4 mm and 5 mm matter
- Cyclists on metric bikes, including 4, 5 and 6 mm
- A van or workshop that needs long straight keys and 10 mm
Not ideal for
- A Torx or other star fastener
- High torque on a ball end, or a hex that is already round
Mistakes to avoid
- 1
Forcing a near-size imperial key
Metric and imperial sizes that are close will start in the wrong socket. If the key wobbles, stop. Rounding the hex is what happens next, and a rounded brake or stem bolt is no longer a home job.
- 2
Using the ball end to crack a tight bolt
The straight end is for full contact on the first and last turn. A ball end is for angle after the bolt is moving. A chamfer is not a ball end, and a maker's angle is not a high-torque rating.
- 3
Trusting the piece count or the torque field
A piece count can include a plastic handle and screwdriver blades. A colour sleeve is useless once the size mark has gone. An Amazon torque attribute on a folding set is not a working capacity.
What to weigh up
Size system and the sizes you will meet
HighThe size system is the first check, because a near miss rounds the fastener. Metric and imperial keys that are close in size will start in the wrong socket. UK bikes are metric. A mixed house needs both systems, in a set that labels them, with the sizes printed rather than a size-system field that names SAE and then lists none. A useful metric spread is 1.5, 2, 2.5, 3, 4, 5, 6, 8 and 10 mm. Home flat-pack often stops at 4 mm and 5 mm.
End, arm and holder
HighThe straight hex is for full contact and for the first and last turn. A ball end is only for reach at an angle after the bolt is moving. Park Tool's note on a ball-end set sold by Halfords is that ball ends are not for high torque. A stated angle, such as 25 degrees, is a maker figure. A chamfer on the tip is not a ball end, and a title that says hex while one bullet says ball end has to be checked in the parcel. A long arm helps in a recess and adds leverage.
Which option suits you?
Three typical situations, each with a recommendation from this comparison.
A metric bike
UK bikes are metric. The core sizes are 4, 5 and 6 mm, with 2, 3 and 8 mm close behind, and you still need to notice Torx. The Stanley folder is the pocket metric set reviewers use on bikes, and it stops at 8 mm.
Van or workshop
You want long straight keys, 10 mm, and a case. A ring at the bottom of this price range is a spare, not the site set. The LOZAGU box prints metric sizes to 10 mm and SAE sizes to 3/8 in. Tighten with the L-key, not the plastic handle.
Common questions about Allen keys
Which Allen key is the top pick in this set?
The top pick in this set is the MULWARK folding metric and SAE set at about £14.99. amazon.co.uk shows 4.7 from 5,474 reviews, the largest sample here, and the listing score is 90. It puts eight metric sizes from 1.5 mm to 8 mm and nine SAE sizes from 5/64 in to 1/4 in in one body with a grip. Check that the parcel matches that hex list. The title also says 2 pack, the keys do not lock, and there is no 10 mm key.
Which Allen key is the best value in this set?
The best value in this set is the Stanley 2-69-264 at about £7.42. It is an eight-piece metric folding set, 1.5–8 mm, and amazon.co.uk shows 4.5 from 4,149 reviews. The listing ranks it 1 in Hex Keys. Reviewers use it on bikes, a bed, a chair and a uPVC door because the body keeps the sizes together. The arms do not lock, the plastic sides flex under load, and the material row says Karton rather than a steel grade. There is no 10 mm key.
How much does an Allen key set cost on amazon.co.uk?
On these amazon.co.uk listings, the two ring sets are about £3.98 and about £3.99. Folding and boxed sets in the middle run from about £7.42 to about £14.99. A long ball-end set is about £19.90, and a sliding T-handle set is about £39.89. Those are the shelf prices used for this comparison, not a promise of the next price. A ring near £4 is a spare for a light job. It is not the set to keep in a van.
Should you buy metric or imperial Allen keys?
Use metric on a UK bike and on most modern flat-pack. Use imperial when the fastener is in an older fitting and a near metric key starts to wobble. Close sizes round the hex. A mixed house needs both systems, printed and labelled, not a size-system field that says SAE while no imperial size is listed. If you are unsure which system the bolt is, stop and measure the socket across the flats rather than forcing the next key up.
When should you use a ball-end Allen key?
Use the straight hex to crack a tight bolt and to finish it. A ball end is for turning at an angle after the bolt is already moving. Park Tool, on a ball-end set sold by Halfords, says ball ends are not for high torque. A maker angle such as 25 degrees is that maker's figure, not a licence to tighten at full force. A chamfer on the tip is not a ball end. If the title and a bullet disagree about the tip, check the key in the parcel.
Does ISO 2936 mean these Allen key sets are certified?
ISO 2936:2014 is the standard for hexagon socket screw keys. It covers dimensions, a proof-torque test, marking and a minimum hardness, and the sample shape is a straight hex. You should not treat any set on this page as certified to ISO 2936 or BS ISO 2936, because the listings do not say so. A chrome vanadium, S2 or SK2 name does not guarantee the key will not round a bolt. An Amazon torque figure on a folding set is not a working capacity.
When should you stop and call a professional?
Call a professional when the hex is already round on a brake, a stem or another safety part, when a seatpost or similar is seized in a frame you cannot afford to scrap, or when the next step is drilling the fastener out and you have not done that before. At work, replace worn keys rather than leaving people to carry on with them. Forcing a near-size imperial key, or using the ball end to break a bolt loose, is how a sound hex gets ruined.
Our verdict
The top pick is the MULWARK folding metric and SAE set. It scores 90, with 4.7 from 5,474 amazon.co.uk reviews, and it keeps both size systems in one body at about £14.99. The metric list stops at 8 mm, and the title also says 2 pack, so match the parcel to the hex size list. The best value is the Stanley 2-69-264, an eight-piece metric folder at about £7.42 with 4.5 from 4,149 reviews. The arms do not lock, the sides flex under load, and there is no 10 mm key.
Best overallView offer
MULWARK folding metric and SAE set
Highest score in this set, with 4.7 from 5,474 reviews and both size systems in one folding body.
Best value
View offer
Stanley 2-69-264 folding set
Highest value score among the rest, at about £7.42, with 4.5 from 4,149 reviews and a metric span to 8 mm.
Editorial
DIY & tools editor
Hand toolsFastenersDIY tools
Peter F. is the editor for DIY & tools at productscompared.co.uk. Comparisons in this category are checked against amazon.co.uk listings, review evidence and public UK sources.
Updated: October 2026
8 sources checked
Guides to Allen keys
Guides on what to look for, how to use a product, and common mistakes.
Allen key buying guideSize system, the sizes you will meet, the end and the holder, in that order.Best Allen keyWho each set in this comparison is for, and who should skip it.How to use an Allen keySeat the straight end and turn without rounding the hex.Allen key metric or imperialHow to tell the two size systems apart and match the fastener.Allen key for bikesMillimetre sizes and Torx on a UK bike.
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Sources
Sources for this comparison, last checked on 22 October 2026.
- ISO 2936:2014, hexagon socket screw keys (retrieved 22 October 2026)
- HSE INDG291, providing and using work equipment safely (retrieved 22 October 2026)
- GOV.UK, General Product Safety Regulations 2005: Great Britain (retrieved 22 October 2026)
- Consumer Rights Act 2015, section 9 (retrieved 22 October 2026)
- Halfords, Park Tool AWS-8 ball-end hex set (retrieved 22 October 2026)
- Halfords basic 6-piece Allen key set (retrieved 22 October 2026)
- Velo, your complete guide to hex keys (retrieved 22 October 2026)
- RDG Tools, Bondhus ball-end hex double pack (retrieved 22 October 2026)
This article contains affiliate links. If you buy through them, we may earn a commission at no extra cost to you. Listings, review counts and public sources still decide the comparison. We did not run a lab test.