CWC band size chart by model: fixed bars and the half-millimetre trap

Cabot Watch Company is the British military contractor whose straps confuse sellers for two separate reasons: nearly every watch ships on fixed bars, so ordinary two-piece straps do not fit at all, and the G10 family splits across a half-millimetre, 18.5mm on four models and 19mm on the GS Sapphire, that retailer tables keep rounding and swapping [7][11]. This chart was built from the cwcwatch.com catalog itself, all 137 products enumerated fresh at build time [1], with every rail quoted verbatim from the product page that prints it and the widths CWC does not print flagged as exactly that: not printed, never guessed.

Quick answer: the four half-millimetre watches (Fatboy-80, T20, Mellor-72, W10) print 18.5mm and ship on 18mm straps. The GS Sapphire family prints 19mm lug width and also ships on an 18mm strap. Every diver-class CWC prints 20mm with 47mm lug-to-lug, as does the G40 family. The standard G10 prints no width anywhere; it ships on an 18mm strap over fixed bars. On all of them the strap must pass through or around fixed bars, so one-piece NATO-style and open-ended straps are the only classes that fit.

The printed rails: every width cwcwatch.com states itself

WatchWidthLug-to-lugCaseRail exactly as printed
GS Sapphire family (8 listings)[11] [12]19 mmnot printed39.5mm incl. crownFixed strap bars 19mm lug width. Supplied on a CWC black 18mm strap
G10 Fatboy-80[7]18.5 mm43 mm38mm incl. crownLug width: 18.5mm. Dimensions: 43mm lug to lug, diameter 38mm (including crown)
T20 General Service[8]18.5 mm42 mm38mm incl. crown18.5mm fixed lug bars. 38mm case (including crown), 42mm lug to lug. Supplied on a Cabot military grey 18mm strap
Mellor-72[9]18.5 mm42 mm38mm incl. crown18.5mm fixed lug bars. 38mm case (including crown), 42mm lug-to-lug. Supplied on a Cabot military grey 18mm strap
W10 Navigator Automatic[10]18.5 mmnot printednot printed18.5mm Fixed bars. Supplied on a Cabot military grey 18mm strap with gloss buckles
G40 family (3 listings)[13] [14]20 mm46 mm40mm (44mm with crown)Fixed strap bars, 20mm lugs. 46mm height lug to lug. Supplied with 20mm grey strap
Diver fleet (21 listings)[15] [23]20 mm47 mm45mm incl. crown47mm lug to lug, 20mm lug width. Fixed strap bars, supplied with 20mm issue strap
6BB-WR automatic chronograph[29]20 mm49 mm42mm (43.5mm with crown)Lug to Lug: 49mm Lug Width: 20mm. Stainless steel with fixed bars
Valjoux 7733 Pilot Chronograph[30]20 mm46 mm40mm incl. crownLug width: 20mm fixed bars for CWC issue military strap. 46mm lug to lug
Cabot Falcon chronograph[31]20 mm46 mm40mm incl. crownStainless steel matte case with 20mm fixed bars. Case dimensions: 40mm width (including crown), 46mm height

Every row above is the verbatim rail from a fresh en-US pull of that product page at build time; the second citation on the three family rows is the sibling check confirming every listing in the family prints the identical rail (all eight GS Sapphires, all three G40s, all 21 diver-class listings). Nothing is converted, rounded or inferred.

The 18.5 versus 19 decoder: the swap in the wild

The half-millimetre split is the reason this table needed to exist. On the maker pages the assignment is unambiguous: the G10 Fatboy-80 prints Lug width: 18.5mm [7], the T20 and Mellor-72 print 18.5mm fixed lug bars [8][9], the W10 prints 18.5mm Fixed bars [10], and the entire GS Sapphire family prints Fixed strap bars 19mm lug width [11]. The strap trade tells it differently: the most-cited strap-retailer guide on CWC straps prints CWC's own specifications confirm: 18.5mm lug width on the standard G10 and GS Sapphire, 19mm on the G10 Fatboy-80 reissue [37], which inverts both families against cwcwatch.com: the GS Sapphire is 19mm, not 18.5mm, and the Fatboy-80 is 18.5mm, not 19mm. The same blog is right about the detail that matters more than any width: the G10's spring bars are welded to the case as part of its MoD specification, so a single-pass through-strap is the correct fit [37]. Buyers who round 18.5 up to 19 for the half-millimetre watches get a strap that fights the fixed bars; the factory answer is the 18mm strap every one of these four ships on.

Fixed bars: the mount decides the strap before the width does

CWC states the policy itself, on a product page: Fixed bars are standard on all CWC models and the Sea Falcon is no exception [22]. That sentence is the whole strap-buying logic for the brand. A two-piece strap that mounts on removable spring bars cannot be fitted, because there are no removable spring bars; the strap must thread between case and bar in one pass, or wrap the bar with an open-ended design. CWC's own premium leather strap page is built around exactly this: Open-ended for use with CWC military fixed bar watches, the leather loop will fit 18mm lug widths (20mm straps are also available as a separate listing) [36]. The divers collection page repeats the hardware in fleet terms: 300m waterproof, Swiss-made using Swiss quartz movements, fixed steel strap bars [3]. And on the titanium Ti300 the brand explains the engineering cost of the policy: Creating a titanium version with the requisite fixed bars required a solution to machine the bars as part of the case [21].

The standard G10: the one width everybody quotes and CWC does not print

The watch most people mean by CWC, the issued G10, is the one row this chart refuses to fill. The current product page prints the case (38mm case including crown, 36.5mm without crown), the movement, the battery hatch, and the strap supply line: Fixed bars, supplied with 18mm grey CWC strap [4]. No lug width appears anywhere on the page, and the same is true of the G10 Navigator [5] and the Pegasus Airborne G10 [6]. The 18.5mm figure that circulates for the standard G10 comes from the surrounding family (four sibling models print it) and from third parties, not from the G10's own page; the strap-retailer guide attributes 18.5mm to the standard G10, and forums and reviews carry the same number for issued examples, but a chart that quotes only the maker cannot print it as a spec. What is first-party and sufficient for a purchase: the watch ships on an 18mm one-piece strap over fixed bars, and the brand's own fixed-bar leather strap for these watches fits 18mm lug widths [36]. The row below says not printed, and means it.

The not-printed list: twelve watches, flagged not guessed

WatchStrap suppliedCase as printedWhat the page actually prints
Standard G10[4]18mm strap supplied38mm incl. crownFixed bars, supplied with 18mm grey CWC strap. The page prints no lug width
G10 Navigator (with Date)[5]18mm strap supplied38mm incl. crownFixed bars, supplied with military issue grey 18mm strap. No lug width printed
Pegasus Airborne G10[6]18mm strap suppliednot printedFixed strap bars for strength and security. Supplied with an 18mm strap in maroon colour. No lug width printed
G22 Automatic[24]not printed38.5mm incl. crown41.1mm lug-to-lug and fixed strap bars printed; no lug width anywhere on the page
Black 80 Automatic Diver[25]20mm strap suppliednot printedFixed strap bars. Supplied with CWC 20mm black strap. No width printed
1980 RN Divers Automatic Re-Issue[26]20mm strap suppliednot printedFixed strap bars. Supplied with 20 mm CWC military grey issue strap. No width printed
1983 Re-Issue RN Divers Quartz[27]20mm strap suppliednot printedFixed strap bars. Supplied with 20mm CWC issue military grey strap. No width printed
SBS Black Ice[28]not printednot printed120-click bezel and fixed steel bars. No width printed
RAF Pilots Quartz Chronograph[32]not printednot printedStainless steel matte case with fixed bars. No width printed
Cabot Fifty Limited Edition[33]not printed18mm lug to lug, as printed38mm diameter including crown 18mm lug to lug. Fixed bars press fit made as they were during WWII. No lug width printed
Cabot Steel Limited Edition[34]not printednot printedFixed bars as per the original specifications. No width printed
ACF Special Edition GS Watch[35]not printednot printedStainless steel case and fixed strap bars. No width printed

Twelve of the 49 watch-class listings in the catalog print no lug width at all. For most of them the supplied-strap size carries the answer (18mm across the G10 family, 20mm across the diver reissues), and the fixed-bar mount carries the strap type. The Cabot Fifty row is printed exactly as the page prints it, including its 18mm lug to lug figure, which reads like a width and is labeled a length; it stays verbatim because verbatim is the rule.

The 47mm diver fleet: one case, twenty-one listings

The divers are the simplest part of the catalog and the easiest to verify, because CWC prints the whole rail in one sentence on nearly every listing: 45mm diameter including crown (41mm excluding crown), 47mm lug to lug, 20mm lug width [15]. The re-issues keep the rail whether quartz or automatic [16], the 1987 SBS re-issue [17] or E9 [18], Arctic Radar [19], Tamar [20] or titanium Ti300 [21], and the collection page states it as a fleet fact alongside the fixed steel strap bars line [3]. One 20mm one-piece strap serves the entire diver wall. The chronographs sit one step outside the fleet with their own prints: the 6BB-WR at Lug to Lug: 49mm Lug Width: 20mm [29], the limited Valjoux 7733 at Lug width: 20mm fixed bars [30], and the Cabot Falcon at 20mm fixed bars [31].

Is there an official CWC band size chart?

No. The maker prints widths scattered across 37 of 49 watch pages in four different wordings (lug width, fixed lug bars, fixed strap bars plus a number, lugs), and prints nothing on the other twelve. watchbands.ai, the largest strap-size database, listed 193 brands at build time with no CWC or Cabot entry [2]. The nearest incumbent is the strap-retailer blog above, which covers the G10 family and the divers, swaps the 18.5/19 assignment, and does not table the GS Sapphire fleet, the G40s, the chronographs or the not-printed list [37]. Third-party reviews corroborate the half-millimetre rail where they touch it: the Mellor-72 review measures fixed spring bars at the 18.5mm lugs and prints Lug Width: 18.5mm in its spec table, matching the maker page [38]. No consolidated first-party chart exists; this page is that table.

How this catalog was counted

The cwcwatch.com products.json endpoint enumerates 137 products in a single page on a fresh pull [1], from watch listings through straps, vault watches, spare parts and apparel. Every one of the 137 product pages was fetched en-US at build time, all HTTP 200. Watch-class listings number 49 (the divers fleet of 21, the GS Sapphire family of 8, the G40 family of 3, the G10 family of 6 across standard, Navigator, Pegasus, Fatboy-80, T20 and Mellor-72, the W10, the G22, and the chronographs and limited editions); 37 of them print a width and 12 print none. The spec block in the served HTML is the same text as the catalog body_html, which did not change a byte between the previous night's pull and this build's. The 63 verbatim quotes this page carries were checked byte-exact against the fresh pulls before any row was published, and no width on this page was inferred from case size, strap slugs or sibling models.

Sources

  1. cwcwatch.com products.json, fresh pull at build: 137 products enumerated in one page; the catalog basis for every row on this page (pass-U pull of the previous night re-diffed: zero body_html changes across the 137): www.cwcwatch.com
  2. watchbands.ai brand index, fresh pull at build (193 brand slugs; root-relative shape probed first, legacy /brands/ pattern returns 0; controls seiko, citizen, rolex present by slug and text; no CWC or Cabot entry): watchbands.ai
  3. cwcwatch.com divers collection page, fresh pull at build: fixed steel strap bars and the fleet rail verbatim (All CWC divers' watches have a 45mm diameter including crown (41mm excluding crown), 47mm lug to lug, 20mm lug width): cwcwatch.com
  4. cwcwatch.com en-US PDP: the standard CWC British Military G10, fresh pull at build. Prints Fixed bars, supplied with 18mm grey CWC strap and 38mm case including crown, 36.5mm without crown, and prints no lug width anywhere on the page: www.cwcwatch.com
  5. cwcwatch.com en-US PDP: G10 Navigator (with Date), fresh pull at build: Fixed bars, supplied with military issue grey 18mm strap; no lug width printed: www.cwcwatch.com
  6. cwcwatch.com en-US PDP: Pegasus Airborne G10, fresh pull at build: Fixed strap bars for strength and security. Supplied with an 18mm strap in maroon colour; no lug width printed: www.cwcwatch.com
  7. cwcwatch.com en-US PDP: G10 Fatboy-80, fresh pull at build: Lug width: 18.5mm and Dimensions: 43mm lug to lug, diameter 38mm (including crown), depth: 13mm approx and Stainless steel case with fixed bars: www.cwcwatch.com
  8. cwcwatch.com en-US PDP: T20 General Service Quartz Watch, fresh pull at build: 18.5mm fixed lug bars, 38mm case (including crown), 42mm lug to lug, Supplied on a Cabot military grey 18mm strap: www.cwcwatch.com
  9. cwcwatch.com en-US PDP: Mellor-72, fresh pull at build: 18.5mm fixed lug bars, 38mm case (including crown), 42mm lug-to-lug, Supplied on a Cabot military grey 18mm strap: www.cwcwatch.com
  10. cwcwatch.com en-US PDP: W10 Navigator Automatic, fresh pull at build: 18.5mm Fixed bars, Supplied on a Cabot military grey 18mm strap with gloss buckles; no lug-to-lug printed: www.cwcwatch.com
  11. cwcwatch.com en-US PDP: GS Sapphire, fresh pull at build: Fixed strap bars 19mm lug width, Supplied on a CWC black 18mm strap, 39.5mm case incl. crown, 36.5mm without crown: www.cwcwatch.com
  12. cwcwatch.com en-US PDP: GS Sapphire sibling check, fresh pull at build: all eight GS Sapphire listings (Black, Stainless, Military Green x2, Desert Storm x2, Subhunter x2) print the identical Fixed strap bars 19mm lug width rail: www.cwcwatch.com
  13. cwcwatch.com en-US PDP: G40 Quartz Watch, fresh pull at build: Fixed strap bars, 20mm lugs, 40mm case (44mm with crown), 46mm height lug to lug, Supplied with 20mm grey strap: www.cwcwatch.com
  14. cwcwatch.com en-US PDP: G40 sibling check, fresh pull at build: the Sonar and Subhunter G40s print the same 46mm lug-to-lug and fixed-strap-bars rail (Sonar: Fixed strap bars 20mm red and black elasticated military strap supplied): www.cwcwatch.com
  15. cwcwatch.com en-US PDP: 1981 RN Diver Automatic Re-Issue, fresh pull at build: 45mm diameter including crown (41mm excluding crown), 47mm lug to lug, 20mm lug width. ... Fixed strap bars Supplied with 20mm CWC issue strap: www.cwcwatch.com
  16. cwcwatch.com en-US PDP: RN Quartz Divers Mk.2 Day/Date, fresh pull at build: 47mm lug to lug. 20mm lug width. ... Fixed bars, supplied with 20mm grey strap: www.cwcwatch.com
  17. cwcwatch.com en-US PDP: 1987 SBS Quartz Diver Re-Issue, fresh pull at build: 47mm lug to lug, 20mm lug width, bezel diameter 40mm ... Fixed strap bars, supplied with 20mm all black Strap: www.cwcwatch.com
  18. cwcwatch.com en-US PDP: E9 Quartz Diver, fresh pull at build: 47mm lug to lug, 20mm lug width ... Fixed bars, 20mm supplied with CWC Land-Sea-Air strap: www.cwcwatch.com
  19. cwcwatch.com en-US PDP: Arctic Radar Quartz Diver, fresh pull at build: 45mm diameter including crown (41mm excluding crown), 47mm lug to lug, 20mm lug width ... Fixed bars, 20mm grey or black strap supplied as standard: www.cwcwatch.com
  20. cwcwatch.com en-US PDP: Tamar Quartz Divers, fresh pull at build: Lug-to-Lug: 47mm Lug Width: 20mm (limited to 100 pieces): www.cwcwatch.com
  21. cwcwatch.com en-US PDP: Ti300 Titanium Diver, fresh pull at build: Lug to lug: 47mm Strap width: 20mm, and the engineering note verbatim: Creating a titanium version with the requisite fixed bars required a solution to machine the bars as part of the case: www.cwcwatch.com
  22. cwcwatch.com en-US PDP: Cabot Sea Falcon Black, fresh pull at build: Fixed bars are standard on all CWC models and the Sea Falcon is no exception, 47mm lug to lug, 20mm lug width, 20mm Fixed bars, supplied with 20mm black strap: www.cwcwatch.com
  23. cwcwatch.com en-US PDP: diver-fleet sibling check, fresh pull at build: all 21 diver-class listings in the catalog (RN81 reissue, RN300/SF300 quartz and automatic, SBS, E9, Arctic Radar, Mutineer, Tamar, Ti300, Sea Falcon) print 47mm lug-to-lug with a 20mm width: www.cwcwatch.com
  24. cwcwatch.com en-US PDP: G22 Automatic, fresh pull at build: 38.5mm diameter including crown 41.1mm lug-to-lug, Stainless steel case with fixed strap bars; no lug width printed: www.cwcwatch.com
  25. cwcwatch.com en-US PDP: Black 80 Automatic Diver, fresh pull at build: Fixed strap bars Swiss-made Supplied with CWC 20mm black strap; no width printed on the page: www.cwcwatch.com
  26. cwcwatch.com en-US PDP: 1980 RN Divers Automatic Re-Issue, fresh pull at build: Fixed strap bars Swiss-made Supplied with 20 mm CWC military grey issue strap; no width printed: www.cwcwatch.com
  27. cwcwatch.com en-US PDP: 1983 Re-Issue RN Divers Quartz, fresh pull at build: Fixed strap bars ... Supplied with 20mm CWC issue military grey strap; no width printed: www.cwcwatch.com
  28. cwcwatch.com en-US PDP: SBS Black Ice, fresh pull at build: the anti-reflective sapphire glass, 120-click bezel and fixed steel bars; no width printed: www.cwcwatch.com
  29. cwcwatch.com en-US PDP: 6BB-WR automatic chronograph, fresh pull at build: Lug to Lug: 49mm Lug Width: 20mm, Stainless steel with fixed bars, preserving the original military style: www.cwcwatch.com
  30. cwcwatch.com en-US PDP: Valjoux 7733 Pilot Chronograph Limited Edition, fresh pull at build: Lug width: 20mm fixed bars for CWC issue military strap, 46mm lug to lug: www.cwcwatch.com
  31. cwcwatch.com en-US PDP: Cabot Falcon Quartz Chronograph, fresh pull at build: Stainless steel matte case with 20mm fixed bars, Case dimensions: 40mm width (including crown), 46mm height: www.cwcwatch.com
  32. cwcwatch.com en-US PDP: RAF Pilots Quartz Chronograph, fresh pull at build: Stainless steel matte case with fixed bars; no width printed: www.cwcwatch.com
  33. cwcwatch.com en-US PDP: Cabot Fifty Limited Edition, fresh pull at build: Fixed bars press fit made as they were during WWII 38mm diameter including crown 18mm lug to lug 12mm thickness; note the page prints 18mm lug to lug, and no lug width: www.cwcwatch.com
  34. cwcwatch.com en-US PDP: Cabot Steel Limited Edition, fresh pull at build: stainless steel case machined in England with fixed bars as per the original specifications; no width printed: www.cwcwatch.com
  35. cwcwatch.com en-US PDP: ACF Special Edition General Service Watch, fresh pull at build: stainless steel case and fixed strap bars; no width printed: www.cwcwatch.com
  36. cwcwatch.com en-US PDP: CWC Premium Leather Strap 18mm, fresh pull at build: Open-ended for use with CWC military fixed bar watches, the leather loop will fit 18mm lug widths (20mm straps are also available as a separate listing); the brand own strap page for fixed-bar watches: www.cwcwatch.com
  37. cnswatchbands.com strap-retailer blog, fresh pull at build: CWC's own specifications confirm: 18.5mm lug width on the standard G10 and GS Sapphire, 19mm on the G10 Fatboy-80 reissue. The nearest thing to an incumbent; disclosed on this page as adjacent, and note its 18.5/19 assignment contradicts cwcwatch.com itself on both families (see the decoder section): cnswatchbands.com
  38. Two Broke Watch Snobs Mellor-72 review, fresh pull at build: fixed spring bars at the 18.5mm lugs and a spec table printing Lug Width: 18.5mm, matching the first-party rail; third-party corroboration, cited as such: twobrokewatchsnobs.com