Strap for Prospex Diver 1970 Scuba Black Series

The lug width of the Seiko Prospex Divers SPB257 is exactly 20 mm. This measurement is precise and tolerant to no deviation: a strap intended for this case must have exactly 20 mm width. To verify compatibility, measure the internal space between the lug pins using a ruler or digital calliper.

For a dive watch like the SPB257, we recommend three choices: a vegetable-tanned alligator strap for formal wear that develops character patina over time; a ballistic nylon NATO for maximum drainage in a marine environment; an FKM (Viton) rubber strap for regular diving practitioners. All are available in the 20 mm width, specifically compatible with this model.

To change the strap, obtain a spring bar tool (spring bar removal pin). Place the watch on a stable surface, insert the bifurcated tip of the tool into the lateral holes of the spring bar, apply controlled pressure until the bar retracts slightly, then extract it. Repeat on the other side. Insert the spring bars into the new strap, ensuring the curved section of the bar faces outward from the case to prevent damage to internal components.

Yes, numerous artisanal straps are compatible with the SPB257 due to its standard 20 mm lug width. At Milano Straps, you will find a complete collection of noble leather straps (alligator, calf, shell cordovan), ballistic nylon NATO options, and FKM rubber choices. All are tested to accommodate the watch's spring bars without play or excessive friction.

A vegetable-tanned leather strap on a dive watch typically lasts 2–4 years if regularly exposed to marine humidity, provided it is dried and treated with beeswax every 6–8 months. If use is predominantly urban, durability extends to 5–7 years. FKM rubber, by contrast, resists marine environments indefinitely but may yellow over time. Ballistic nylon NATO has the longest lifespan of the three, resisting chlorine, salt, and UV for 8–10 years of daily use.