Casio
Casio F-91W Strap Size — 18mm Lug Width
The Casio F-91W has a 18mm lug width, so it takes a 18mm watch strap.
Lug width18mm
| Lug width | 18 mm |
|---|---|
| Case size | 38.2 mm |
| Lug-to-lug | 37 mm |
| Thickness | 8.5 mm |
| Spring bar Ø (typical) | 1.5 mm |
| End type | Straight |
Strap styles that fit
- NATO / Zulu18mm fits if the strap's thickness clears the case under the bars.
- PerlonWoven pass-through, 18mm.
- 2-piece leatherStraight ends fit flush.
- Rubber / siliconeDivers & sports fit well.
- Milanese / meshStraight-end 18mm mesh fits.
- Metal braceletNeeds 18mm end-links shaped for this case.
▲ One-piece feel — single-pass straps work best.
Fit & sizing notes for the F-91W
- Width: buy 18mm straps. Tapered straps listed as 18/16mm or 18/14mm fit too; only the first number has to match. See strap sizes explained.
- Spring bars: 18mm long, about 1.5mm diameter (spring bar sizes).
- Wrist fit: at 37mm lug-to-lug it should sit within the top of wrists from about 12.3cm up (rule of thumb: lug-to-lug under ~30% of wrist size). That's longer than 1% of the watches in our index. See what size watch suits your wrist.
- Strap thickness: at 8.5mm thick it's a slim case: thin leather (about 2.5–3mm) or a single-pass strap keeps it low; a regular NATO adds 1–2mm underneath.
Sources & corrections
Lug width from widely published specifications. Case sizes and references vary, so measure your own watch if anything looks different.
Spec wrong for your watch? Send us a correction with your reference number.
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Casio F-91W — strap questions
What size strap does the F-91W take?
The Casio F-91W has a 18mm lug width, so you need a 18mm watch strap.
Will any 18mm strap fit the F-91W?
Most will. Width is the main thing to match, but also check that the strap's spring-bar holes suit the bars, and that the strap is thin enough to clear the case between the lugs. A metal bracelet needs 18mm end-links made for this model.
What spring bar size does the F-91W use?
18mm long and about 1.5mm in diameter (a typical figure; measure the original bar to be sure).
Is the F-91W good for strap swapping?
Yes. With standard 18mm spring-bar lugs, NATO, leather, rubber and mesh straps can all be fitted with a spring-bar tool.