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Adjustable spanner size: the opening comes before the length

Updated: 22 October 2026

You are comparing two amazon.co.uk listings that both say 200 mm, and you still cannot tell which jaw will fit the nut. Adjustable spanner size is that mix-up: the number on the handle is the length, and the opening is a separate figure that several listings print twice and do not agree on. Buy the opening in millimetres first, then check for play, then choose the length, and treat a conflicting second field as unknown. The [adjustable spanner comparison](/hub/hand-tools/adjustable-spanner) holds the twelve tools and the captured prices. A named pick belongs on the [best adjustable spanner](/hub/hand-tools/adjustable-spanner/sub/adjustable-spanner-best) page. A purchase through our links may earn a commission at no extra cost to you.

You are comparing two amazon.co.uk listings that both say 200 mm, and you still cannot tell which jaw will fit the nut.

Our top picks

Bahco Bahco 80 series 3-piece set

Best overall

Bahco Bahco 80 series 3-piece set
8.6/10about £39.99
View offer
Stanley Stanley 200 mm adjustable wrench

Best value

Stanley Stanley 200 mm adjustable wrench
8.4/10about £7.99
View offer
Shall Shall 3-piece adjustable wrench set

Rank 3

Shall Shall 3-piece adjustable wrench set
6.5/10about £16.99
View offer
On this page
  1. 1.The number on the handle is the length
  2. 2.What a millimetre opening has to cover
  3. 3.Play, face and steel words
  4. 4.A check order for this set

The number on the handle is the length

What people still call a shifter is one fixed jaw and one jaw on a worm screw, with the stamped size running along the handle. In ISO 6787:2018 that stamp is the nominal length, not the gap between the jaws. A 200 mm tool is the usual single, and that figure is still not an opening. The openings this capture prints are narrower than the handles. Navegando states 6–19 mm. Shall states 23.8 mm, 28.6 mm and 35 mm. WORKPRO states 42 mm. MAXPOWER's bullet states 40 mm, while its jaw-capacity field states 16 inches, which repeats the length. Stanley's 0-90-948 bullet says 24/200 mm and the jaw field says 8 inches. Bahco prints 155, 205 and 255 mm and no opening. Where a second field fights the first, leave it unknown.

What a millimetre opening has to cover

ISO 6787:2018, adopted in the UK as BS ISO 6787:2018, sets a minimum for the largest opening at each nominal length. In the sample of Table 1 those minima are 19 mm at 150 mm, 24 mm at 200 mm, 27 mm at 250 mm and 34 mm at 300 mm. None of the twelve listings print the mark, so the row is a ruler beside a bullet, not a badge on any ASIN here. A trade guide, not these listings, puts a typical 200 mm jaw near 24–27 mm and a wide jaw near 38 mm, as a rule of thumb. Compression nuts and the stop at gas belong on the adjustable spanner for plumbing page.
Bahco Bahco 80 series 3-piece set

Testsieger

Bahco Bahco 80 series 3-piece set
8.6/10about £39.99
View offer

Play, face and steel words

Jaw play is slack in the movable jaw when the worm should hold it still. Close the jaws and try to rock the moving face. A flop means the flats walk off the nut. On amazon.co.uk you look for the same complaint repeating. Cheaper 150 mm tools, the Shall set and the Stanley 6 inch draw slack comments. Bahco reviews, 4.7 from 2,151, praise small free play. A printed opening does not prove a tight worm. Smooth jaws belong on chrome nuts and brass. Teeth belong on round or already damaged work. WORKPRO is the reversible toothed jaw here. Chrome vanadium is a steel claim, not a tight worm. A 2.3 from three reviews cannot carry a size the listing never printed.

A check order for this set

Read the opening in millimetres before anything else. If two fields disagree, as they do on Stanley 0-90-948, Stanley 0-90-947 and the MAXPOWER capacity box, treat the opening as unknown. If the listing prints no opening, you are choosing length and review count, and you should check the jaw in your hand. When the nut is tight, soft or already damaged, a ring or a socket is the safer tool, which is the argument on the adjustable spanner vs combination spanner page.

Common questions

Is a 200 mm adjustable spanner a 200 mm opening?
No. On an adjustable spanner, 200 mm is the nominal length. The opening is a separate capacity, and if the tool followed ISO 6787:2018 the minimum largest opening at that length would be 24 mm. A Stanley 0-90-948 bullet can say 24/200 mm while the jaw-capacity field says 8 inches, which repeats the handle. If the fields fight, treat the jaw width as unknown.
What opening should a 150 mm and a 200 mm jaw have at minimum?
If a spanner followed ISO 6787:2018, Table 1 sets the minimum maximum opening at 19 mm for 150 mm nominal length and 24 mm for 200 mm. The same preview gives 27 mm at 250 mm and 34 mm at 300 mm. BS ISO 6787:2018 is the UK adoption. None of these twelve listings print the mark, so the numbers are a ruler, not a compliance claim.
Why do two fields on the same listing disagree?
A jaw-capacity box sometimes receives the handle length, so you see 8 inches next to a 24/200 mm bullet, 24 inches next to a 24/150 mm bullet, or 16 inches next to a 40 mm bullet. Those pairs are not two measurements of the same gap. Leave the conflicting field unknown rather than as the larger number. We did not remeasure the metal.
What is jaw play, and how do you check it before you buy?
Jaw play is rock in the movable jaw when the worm should be holding it. Close the jaw and try to tilt the moving face. A flop means the flats will not stay seated. We did not measure that gap. Slack repeats on cheaper short tools, while Bahco comments praise small free play.
Does chrome vanadium mean the jaw is tight?
No. Chrome vanadium describes the steel. It says nothing about worm clearance or how far the jaw opens. Judge tightness by rocking the jaw, or by a comment that repeats, not by the alloy word in the title.
When is a 150 mm adjustable spanner enough?
A 150 mm tool is enough when the nut is small and you can read an opening around 19 mm, or 6–19 mm as Navegando prints it. It is too short when the flats are wider than that gap. A 200 mm single is the usual next length if the jaw does not spring.

Related pages

Adjustable spanner how to use

Adjustable spanner

Best adjustable spanner for a tight jaw or a low price

Adjustable spanner for plumbing on 15 mm and 22 mm

Adjustable spanner vs combination spanner, when to switch

Sources

Public UK sources listed in the research digest for this comparison. Shelf prices and star lines are the amazon.co.uk figures in the product display.

  1. ISO 6787:2018, adjustable wrenches (retrieved 22 October 2026)
  2. BS ISO 6787:2018 (retrieved 22 October 2026)
  3. HSE: Provision and Use of Work Equipment Regulations (PUWER) (retrieved 22 October 2026)
  4. Gas Safety (Installation and Use) Regulations 1998, regulation 3 (retrieved 22 October 2026)
  5. Gas Safe Register: home improvements (retrieved 22 October 2026)
  6. Consumer Rights Act 2015, section 22 (retrieved 22 October 2026)
  7. Consumer Rights Act 2015, section 9 (retrieved 22 October 2026)
  8. BuildWiz: adjustable wrench (trade guide) (retrieved 22 October 2026)