For as long as the F-91W has existed, one small ritual has followed it around the enthusiast world. You buy the cheap little Casio, you wear it for a while, and then you pop off the resin strap and thread the case onto a NATO or a fabric band you grabbed for a few dollars. Whole communities have formed around the practice, including a subreddit with thousands of members devoted to exactly this. So there’s something almost funny about Casio deciding, after decades, to sell you that modification straight from the factory. That watch is the new Casio F-91WF.
The base watch has been in production since the late 1980s, and its appeal has never really been in question. It’s light, it’s accurate, it costs almost nothing, and it disappears on the wrist. The one recurring complaint has always been the strap, which does its job but rarely inspires much love. That’s the gap the aftermarket filled, and it’s the same gap Casio just addressed itself with the DW5600MNC square earlier this year.
By now I half expect to find a Casio product manager lurking on r/F91Ws_on_NATOs with a burner account, taking notes on everyone’s strap builds. Instead of leaving the fun to the mod crowd, it’s productizing the mod.
Mechanically, nothing here is new. The F-91WF runs the same Module 593 that has powered the F-91W for years. You get a stopwatch, a daily alarm, an auto-calendar, and that dim green LED that reads more as a gesture than a real backlight. Casio quotes a seven-year run on a single CR2016 cell and a weight of 21 grams, which is essentially identical to what a standard resin-strapped F-91W weighs. The cloth band is made from recycled PET, and Casio calls it scratch and stain resistant, sized for wrists from 145 to 215mm. On water resistance, the company keeps things vague, listing the watch simply as water resistant with no depth rating on the product page.
Three colorways have surfaced so far, in black, navy, and olive drab. Casio pitches the WF as a watch that moves from daily life to the trail, though the capability hasn’t changed. Anyone shopping for a serious trail watch was always going to reach for a G-Shock or a Pro Trek instead. Price is the fuzziest part of the story. Casio hasn’t announced a US figure but I’m guessing this will be priced a little higher than the base model. If so, that makes you wonder why you wouldn’t just buy a standard F-91W and a cheap strap.
As someone who keeps a couple of these in the rotation, I’ll admit the factory version has a certain appeal. There’s a tidiness to a strap built for the case rather than borrowed from a parts bin. Whether that’s worth paying up for, when the charm of the F-91W has always been how little it asks of you, is the part I can’t settle. What I’m watching more closely is whether this is a one-off or the start of Casio treating the F-91 line the way it now treats the square. If the mod scene keeps writing Casio’s roadmap, there are worse ways for a brand to spend its time.
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Michael Peñate is an American writer, photographer, and podcaster based in Seattle, Washington. His work typically focuses on the passage of time and the tools we use to connect with that very journey. From aviation to music and travel, his interests span a multitude of disciplines that often intersect with the world of watches – and the obsessive culture behind collecting them.