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How to choose a thumbturn euro cylinder

Updated: October 2026

The old barrel is on the kitchen table, or you are still on amazon.co.uk with the door shut, and the picture shows a knob on one end. A thumbturn euro cylinder puts a key on the outside and a turn on the inside, in the profile a multipoint lock already uses. Before you compare prices, settle the knob on the inside, a split that matches both sides of the door, and whether any security claim is a mark you can name. The [knob cylinder comparison](/hub/hot-water/knob-cylinder) tables four listings from 19 October 2026. We did not run a lab test. A qualifying purchase through our links can earn a commission at no extra cost to you.

The old barrel is on the kitchen table, or you are still on amazon.co.uk with the door shut, and the picture shows a knob on one end.

Our top picks

GANZTECH GANZTECH 30/40T chrome

Best overall

GANZTECH GANZTECH 30/40T chrome
8.6/10about £10.99
View offer
Valorada Valorada 55/45T thumb turn

Rank 2

Valorada Valorada 55/45T thumb turn
5.5/10about £13.99
View offer
BGS BGS 85290 rotary knob 45/45

Best value

BGS BGS 85290 rotary knob 45/45
8.3/10about £6.55
View offer
On this page
  1. 1.What you are buying
  2. 2.Size before brand
  3. 3.Function before the security adjectives
  4. 4.What the four listings do not show

What you are buying

A thumbturn euro cylinder is a replacement barrel, not a new lock. The gearbox, hooks and handles stay on the door. The hub label is Hot water. The turn lets you leave without hunting for a key. That helps on a final exit, and it is a problem if someone outside can reach the knob. British Standard 8621 describes an assembly opened by a key from outside and by a thumbturn from inside. Fitting one of these cylinders does not make the door BS 8621 or PAS 24.

Size before brand

Measure from the centre of the fixing screw, outside and inside as two lengths, in 5 mm steps, and leave the knob off the tape. Home Secure Shop's guide sets that method out. Across one retailer's recent orders, about 27 percent were 35/35 and more than four in ten were offset. Seventy millimetres is not 35/35. Thirty-five plus 35 is 70 mm, and so is 30 plus 40. Sellers do not all print the T on the same side. The outside end should finish flush with the handle, or within 3 mm of it, the figure on an ERA fitting sheet. West Yorkshire Police say not to leave a euro cylinder proud of the handle. Measuring on the open door sits on how to fit a knob cylinder.
GANZTECH GANZTECH 30/40T chrome

Testsieger

GANZTECH GANZTECH 30/40T chrome
8.6/10about £10.99
View offer

Function before the security adjectives

Choose a knob or a key on the inside before you read anti-snap, anti-bump or anti-pick. A thumbturn opens the door with nothing in your hand. A double cylinder, sold as key both sides, needs a key inside as well. The Door and Hardware Federation splits that choice between escape and reach-through. If a letterbox, a pane or a hole lets a hand onto the knob, keyless exit is the weaker function. The longer comparison is thumbturn or key both sides. Cheshire Fire and Rescue's guidance for houses in multiple occupation says final exits and bedsit doors should open without a removable key, and it names a thumb-turn. That is advice for those exits, not every uPVC door. If yours is a fire door, or an HMO exit you do not manage, call a locksmith.

What the four listings do not show

None of the four amazon.co.uk cylinders prints TS 007, a Kitemark or Sold Secure. West Yorkshire Police describe an upgrade as a TS 007 3-star cylinder, or a 1-star cylinder with 2-star security furniture, or Sold Secure Diamond under SS312. A bullet that only says anti-pick is not that mark. What the mark has to show is on TS 007 and a knob cylinder. On 19 October 2026 the four ran from £6.55 to £13.99. The RUCUDIM bullets and one Valorada bullet disagree about whether a knob is fitted. A named 3-star thumbturn means leaving this set.

Common questions

How do I measure a thumbturn without including the knob?
Measure from the centre of the fixing screw to the outside face, then from the same screw to the inside face, and do not run the tape over the knob. Record both lengths in 5 mm steps, as Home Secure Shop's guide describes. The knob sits proud of the door and is not part of the barrel that has to match the lock. Include it and the cylinder you order can stand proud where a snapping attack can grip it.
Is 70 mm the same as 35/35?
No. Seventy millimetres is only the total. A 35/35 cylinder and a 30/40 cylinder can both add up to 70 mm, and they do not put the fixing screw in the same place. Order the two sides you measured, not the sum in a title. An equal 45/45, which is one size in this comparison, is a different door again.
Which number is the inside on a 55/45T title?
You cannot tell from the letter T alone. Sellers do not all hang that letter on the turn side. In this set, 55/45T on the Valorada listing and 30/40T on the GANZTECH listing are sizes, not ratings. Check the product text, or the old cylinder in your hand, for which measurement is the knob. If the listing will not say, do not guess.
What should I check before I add one to the basket?
Confirm the knob will be on the inside, write down both measurements from the screw, and read whether the listing is actually a thumbturn. The RUCUDIM title and bullets disagree, and one Valorada bullet says the thumb turn is not included. Then look for a named mark if this is a front door. Stop if the key will not turn, or if the door is a fire door or an HMO exit you do not manage.
When is a £30 to £55 named 3-star thumbturn the rational order?
When you have already chosen a thumbturn, measured both sides, and the door is a final exit that should meet the upgrade West Yorkshire Police describe. On 19 October 2026, named options outside this comparison included Yale Platinum Ultra from £34.39 and an Avocet ABS Quantum at £54 described as 3-star and Sold Secure Diamond. The spend is wasted if a letterbox means you needed a key on both sides. It does not make the whole door BS 8621.

Related pages

Best knob cylinder

Knob cylinder

How to replace a euro cylinder without locking yourself out

TS007 3 star thumbturn: what the listing must show

Thumbturn or key both sides: which cylinder to order

Sources

Public UK sources named below. amazon.co.uk prices, stars and review counts on these four listings were read on 19 October 2026. Page updated 21 October 2026.

  1. West Yorkshire Police euro cylinder advice (retrieved 19 October 2026)
  2. Secured by Design: locks and associated hardware (retrieved 19 October 2026)
  3. DHF thief-resistant lock assemblies (retrieved 19 October 2026)
  4. DHF TS 007 star ratings (retrieved 19 October 2026)
  5. BSI BS 8621:2017+A1:2024 (retrieved 19 October 2026)
  6. Cheshire Fire and Rescue: houses in multiple occupation (retrieved 19 October 2026)
  7. ERA fitting instructions (retrieved 19 October 2026)
  8. Checkatrade: changing a uPVC door lock (retrieved 19 October 2026)
  9. amazon.co.uk listings B0D5HY325L, B0CLV6BMNX, B0GS5VFV7S and B0H14R6SPH (retrieved 19 October 2026)