The F-91W has been in production since 1989 and its one real weakness was always the strap: resin, which goes sweaty on a long walk. The F-91WF swaps in woven fabric — the modification collectors have been doing themselves with $5 NATO straps for years, now made official. Everything else carries over unchanged: 35.2mm case, 8.5mm thick, 30m water resistance, stopwatch, alarm, and a CR2016 rated for seven years.