You need your watch's lug width — the gap in millimetres between the two horns where the strap attaches. It's usually printed on the case back or listed in your watch's manual. Common sizes are 18mm, 20mm, and 22mm. This strap is 20mm. Not sure? Use our size guide — it takes under a minute.
Tip: when in doubt, go smaller. A slightly narrower strap always fits — a wider one never will.