Strap for Seamaster Diver 300M Master Co-Axial 42 Bronze Gold / Black / Bracelet

The lug width of the Seamaster Diver 300M reference 210.90.42.20.01.003 is 20 millimetres. It is measured from the centre of one hole to the other on the case. This dimension ensures compatibility with all straps designed for the 20mm standard, guaranteeing stable anchorage proportionate to the 42mm diameter case.

For this model we recommend genuine alligator if you desire formal elegance that contrasts with the brushed aluminium, or structured calf for daily wear that will develop a natural patina over time. For underwater and sports use, shell cordovan offers extreme durability. Vegetable-tanned leather in natural colour is the most versatile choice, suitable for both formal and casual contexts.

The strap is changed by releasing the spring bars (the small metal cylinders) that connect the case lug to the old strap. Using a dedicated tool (spring bar tool), press downward one of the small pins to free the strap end, then fully extract the spring bar. Repeat the operation on the other lug. Insert the new 20mm strap aligning the holes, and reposition the spring bars until they click into place.

Yes, quality aftermarket straps with 20mm lug width are perfectly compatible with your Seamaster. In fact, many collectors choose artisanal straps because they offer materiality and finishes impossible to find in the OEM market. Our atelier offers customisable straps in genuine leather (alligator, calf, shell cordovan, vegetable-tanned) with adjustments in sizing and choice of stitching thread.

The duration depends on the material, use and maintenance. A structured calf strap of artisanal quality lasts on average 3-5 years with daily wear. Shell cordovan, thanks to its natural density, can exceed 7-8 years. Quality alligator is maintained for 4-6 years. Vegetable-tanned leather matures with the years, becoming more beautiful and robust. All our straps include an 18-month warranty against manufacturing defects.