Sinn
Diving Watches 403.031— lug 22mm

The lug width of the Sinn 403.031 is 22mm. This is the width of the attachment between the two mounting points on the case. It is important not to confuse this measurement with the crown diameter or case thickness. To verify correctly, measure the vertical distance between the case lugs where the strap fastens.

For the 403.031 we recommend: alligator with vegetable tanning for formal contexts, calf leather for daily use, NATO in regenerated yarns for professional diving, sponge rubber or silicone for saltwater environments. The choice depends on intended use: leather offers elegance, rubber guarantees maximum water durability.

Position the watch on a soft surface. Use a spring bar removal tool to gently push the small retention spring inside each lug. The strap will come out easily. Insert the new strap by aligning the holes with the spring bars and press until you feel the spring retention click.

Yes, any strap with a 22mm lug width is compatible with the Sinn 403.031. High-quality artisanal straps offer greater aesthetic and constructive customisation than original straps, whilst maintaining full mechanical compatibility.

A quality leather strap with vegetable tanning lasts on average 3–5 years if rotated with other straps, or 18–24 months if worn daily. Durability depends on moisture exposure, frequency of immersion, tanning quality and regular maintenance. Rubber or silicone straps have greater longevity in wet environments.