23mm Watch Bands
23mm is the most specialised lug width in the CNS range — sitting between the standard 22mm and 24mm sizes, it exists almost exclusively to serve one specific watch: the Blancpain Fifty Fathoms 45mm. The Fifty Fathoms is one of the most significant dive watches ever made — the reference that established the modern dive watch category in 1953 — and its 23mm lug width is a specific design dimension of that case. Most strap retailers do not stock 23mm at all, leaving Fifty Fathoms owners with no properly fitting alternative to the original strap. CNS Watch Bands stocks 23mm as a dedicated size across sailcloth, leather, and rubber specifically for this reference and the small number of other watches that share this lug width.
Is 23mm the Right Size for Your Watch?
23mm refers to the lug width — the gap in millimetres between the two lugs on your watch case where the spring bars sit. Confirm by measuring with a digital caliper before ordering — at 23mm, the difference between this size and 22mm or 24mm is small but meaningful.
Watches that use 23mm lugs include:
Blancpain Fifty Fathoms 45mm — the primary reference at this lug width. The Blancpain Fifty Fathoms 45mm Automatique and its colour variants use 23mm lugs with standard spring bars. The CNS 23mm strap fits directly with a standard spring bar tool — no specialist equipment required beyond what is used for any other strap change.
Blancpain Fifty Fathoms Bathyscaphe 43mm — some Bathyscaphe variants also use 23mm lugs. Confirm your specific reference before ordering.
If you own the Blancpain x Swatch Scuba Frogskin — this is not a 23mm watch. The Blancpain x Swatch uses approximately 21.7mm lugs compatible with 22mm straps, and uses screw-in pins requiring a 0.9mm hex key rather than conventional spring bars. See the MoonSwatch straps page for full fitting guidance.
Other watches — a small number of vintage references and specialist dive watches from other manufacturers use 23mm lugs. If you have measured 23mm precisely on a watch other than the Blancpain Fifty Fathoms, you are in the right place — the CNS 23mm straps fit any watch with standard 23mm spring bar lugs.
The Blancpain Fifty Fathoms — Why 23mm Matters
The Blancpain Fifty Fathoms is not simply a dive watch that happens to use 23mm lugs. It is the dive watch — the reference that defined the category's design language in 1953, issued to the French naval commando units CASM and later to other elite military diving units worldwide. The Fifty Fathoms established the 300m water resistance standard, the unidirectional bezel, the luminous dial, and the rotating bezel safety mechanism that became the template for every serious dive watch that followed.
A watch with this heritage deserves a strap that matches its quality and considers its specific proportions. The 23mm lug width is not an accident — it is a deliberate design dimension that produces a specific visual relationship between the case and the strap. A 22mm strap on a 23mm lug leaves visible gaps at the lug faces; a 24mm strap will not fit between the lugs at all. The correct size is 23mm, and the correct starting point for strap selection is a retailer who stocks it.
23mm Watch Bands by Material
Sailcloth at 23mm — the most historically resonant and most widely admired strap choice for the Blancpain Fifty Fathoms. The sailcloth strap at 23mm connects the watch to the maritime and nautical heritage of its original operational context — both the material and the watch share a connection to the ocean and to precision engineering for demanding conditions. The technical woven fabric is water-resistant, UV-stable, and quick-drying, making it the most practically appropriate fabric choice for a watch rated to 300m. CNS produces the 23mm sailcloth strap in navy, black, grey, and olive colourways — the colours that suit the Fifty Fathoms' serious, purposeful aesthetic most naturally.
Leather at 23mm — for Fifty Fathoms owners who wear the watch in smart-casual and formal contexts rather than actively diving. Classic flat calfskin and padded calfskin at 23mm in dark brown and black suit the Fifty Fathoms' case proportions and heritage character in office and smart-casual contexts where sailcloth or rubber would read as too casual.
- Padded dark brown calfskin — the most widely worn leather combination for the Fifty Fathoms. The padded profile suits the substantial case depth of the 45mm reference; dark brown leather complements the warm dial tones across the Fifty Fathoms colour range.
- Classic black calfskin — the most formal leather option. Black smooth calfskin on the Fifty Fathoms suits business and smart-formal contexts where the watch's presence is appreciated but a more formal strap is appropriate.
- Vintage two-stitch cognac — for collectors who want to reference the Fifty Fathoms' 1950s heritage through the strap. Cognac two-stitch calfskin at 23mm suits the vintage-inspired character of the watch's heritage design directly.
Rubber at 23mm — for active diving and water use. FKM rubber at 23mm is the most practically correct choice for the Fifty Fathoms worn in the water — the material the watch was designed to be used with in its intended operational context. Water-resistant, maintenance-free, and proportionally suited to the large, deep case. Tropical style rubber at 23mm references the 1960s rubber straps originally issued on dive watches of the Fifty Fathoms era.
Nylon single-pass at 23mm — the original military single-pass nylon at 23mm for casual and outdoor use. Less commonly requested for the Fifty Fathoms than sailcloth or rubber, but available across the CNS colour range for collectors who want the single-pass security construction in fabric.
Strap Recommendations by Context
The Blancpain Fifty Fathoms is a watch that crosses contexts — it was designed for operational diving but is most commonly worn today as a collector piece in everyday and smart-casual settings. Here is how to choose by context:
Active diving and water use — FKM rubber at 23mm. Fully waterproof, maintenance-free, and appropriate for the pressures of diving. The material that matches the watch's design intent.
Everyday casual and outdoor — sailcloth at 23mm. Water-resistant, UV-stable, and heritage-connected. The most considered casual choice for a watch with the Fifty Fathoms' nautical and military heritage.
Smart-casual and office — padded dark brown calfskin at 23mm. The substantial padded profile suits the Fifty Fathoms' case depth and size; the warm brown tone is the most versatile leather colour for a watch worn in varied smart-casual contexts.
Formal occasions — black smooth calfskin at 23mm. The most formal leather option for a watch that crosses from active to formal use.
Heritage collector wear — vintage two-stitch cognac at 23mm or tropical style rubber. Both reference the 1950s–1960s heritage of the Fifty Fathoms' original operational context.
The Blancpain x Swatch — Important Clarification
The Blancpain x Swatch Fifty Fathoms Scuba Frogskin is a different watch from the genuine Blancpain Fifty Fathoms and uses a different strap size and fitting mechanism:
- Strap size: approximately 21.7mm lugs — compatible with 22mm straps, not 23mm
- Fitting mechanism: screw-in pins requiring a 0.9mm hex key — not conventional spring bars
- Correct page: MoonSwatch straps — which covers both the Omega x Swatch MoonSwatch and the Blancpain x Swatch in full detail
If you own the Blancpain x Swatch rather than the genuine Blancpain Fifty Fathoms, you need 22mm straps and a 0.9mm hex key — not 23mm straps and a spring bar tool.
Colour Guide for 23mm Watch Bands
Navy — the most natural sailcloth colour for a nautical and dive watch heritage. Navy sailcloth at 23mm on the Blancpain Fifty Fathoms references the French naval commando heritage of the original watch directly.
Black — the most versatile colour across all materials at 23mm. Black sailcloth, rubber, or leather suits every Fifty Fathoms dial colour and case finish.
Dark brown — the most characterful leather colour at 23mm. Suits the warm dial tones of the Fifty Fathoms colour range in smart-casual contexts.
Grey — the most understated 23mm colour. Grey sailcloth or rubber reads as quietly considered — the colour that says the watch is the statement, not the strap.
Olive — the most operational 23mm colour. Olive sailcloth or nylon references the military and outdoor heritage of the watches originally issued with olive-coloured equipment.
Fitting Your 23mm Strap
The Blancpain Fifty Fathoms 45mm uses standard spring bars — the same fitting mechanism as any other watch with conventional lugs. A standard spring bar tool is all that is required. CNS 23mm straps ship with quick-release spring bars, meaning the spring bar tool is not needed to fit the CNS strap — the quick-release mechanism allows tool-free installation.
Note: the Blancpain x Swatch uses screw-in pins, not spring bars. This guidance applies to the genuine Blancpain Fifty Fathoms only.
Sizing Reference
| Lug Width | Key Watch |
|---|---|
| 22mm | Tudor Pelagos, Marathon GSAR, Blancpain x Swatch |
| 23mm | Blancpain Fifty Fathoms 45mm |
| 24mm | Panerai Luminor 44mm and 47mm |
Frequently Asked Questions
What size strap does the Blancpain Fifty Fathoms take? The Blancpain Fifty Fathoms 45mm Automatique uses 23mm lugs with standard spring bars. CNS stocks 23mm straps in sailcloth, leather, and rubber specifically for this reference. The strap fits with a standard spring bar tool or tool-free with CNS quick-release spring bars.
What is the difference between the Blancpain Fifty Fathoms and the Blancpain x Swatch strap size? The genuine Blancpain Fifty Fathoms 45mm uses 23mm lugs with standard spring bars. The Blancpain x Swatch uses approximately 21.7mm lugs compatible with 22mm straps, and uses screw-in pins requiring a 0.9mm hex key. They are different watches with different strap sizes and different fitting mechanisms.
Why is 23mm so hard to find? Most strap retailers stock only the most popular sizes — 18mm, 20mm, 22mm, 24mm — and skip 23mm as a niche size. This leaves Blancpain Fifty Fathoms owners without a properly fitting alternative to the original strap. CNS stocks 23mm as a dedicated size specifically to serve Fifty Fathoms owners.
What is the best strap for the Blancpain Fifty Fathoms? It depends on the context. For active diving: FKM rubber at 23mm. For everyday and outdoor use: sailcloth at 23mm — the most heritage-connected casual choice. For smart-casual: padded dark brown calfskin at 23mm. For formal: black smooth calfskin at 23mm.
Can I use a 22mm strap on the Blancpain Fifty Fathoms? A 22mm strap on a 23mm lug will leave visible gaps at the lug faces — the strap sits narrower than the lug opening and the gap is visible and proportionally incorrect. The correct size is 23mm. CNS stocks it as a dedicated size so there is no need to compromise.