Before your first watch mod
A few checks before ordering can save a lot of fiddling later.
Start with the exact model
Read the model marking on the case back and compare it with your original packaging or manufacturer’s page. The case marking identifies the watch, but it does not establish that an aftermarket part fits.
| Watch | Documented options | Do not assume |
|---|---|---|
| F-91W | NATO adapters or fitted Vario leather | Every 18mm strap or adapter will fit |
| F-94W | Backlight spreader | Every F-91W part fits this module |
| AE-1200 | Metal case build record | A similar case photo identifies the replacement |
| MDV-106 | Marlin bracelet | Fit on the MDV-10 or every Duro variant |
Three pins that do different jobs
- Factory strap push pin
- The original F-91W straps in these builds use push pins. I removed them with a supported pin punch and small hammer, following the arrow direction.
- Spring bar
- A spring-loaded bar attaches a strap to the lugs. The quick-release versions shown have a small lever. They do not make a factory push pin spring-loaded.
- Bracelet sizing pin
- The Marlin bracelet uses push-out pins to remove links. Follow the direction and instructions for the actual bracelet you receive. These are separate from the bars attaching it to the watch.
What does the quoted width mean?
The F-91W NATO build uses an 18mm to 20mm adapter and a 20mm strap. The strap matches the adapter’s outer width. Case shape, spring-bar position and adapter construction still matter. Width alone is not a compatibility promise.
Choose a sensible first build
An external strap change avoids opening the case, though original push pins can still be awkward. The F-94W diffuser involves the LCD and zebra connector. Read the whole guide and maker instructions before deciding whether that job suits you.
Make a complete budget
- Mark the parts and suitable tools you already own.
- Check the exact seller variant and enter current quotes in one currency.
- Add shipping, tax, consumables and any missing tools to other costs.
- Keep unpriced items visible. A subtotal is not the final cost.
The planner does not convert currencies, verify prices or place orders. Your saved plan stays in this browser.
What happens to water resistance?
None of these modified watches has a documented post-mod pressure-test result here. A shower observation is not a water-resistance rating. Case opening, seals and the assembled case need their own checks. Ask a qualified watch repairer about testing if you rely on water resistance.
Casio’s water-resistance care guidance ↗, checked 12 October 2026.
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