Strap for Seamaster Aqua Terra 150M Master Co-Axial 38.5 Stainless Steel / Diamond / MOP / Bracelet

The lug width of the 231.15.39.21.55.001 model is 20mm. This is the internal distance between the two lugs of the case. You can verify it by inserting a digital caliper between the lugs, perpendicular to the case. It is essential to check this measurement before ordering an aftermarket strap, as a 2mm error would render the strap incompatible.

Vegetable-tanned alligator represents the most elegant and durable choice, as its squared texture naturally complements the teak-pattern dial. For those seeking versatility, quality vegetable-tanned calf develops a unique stratified patina over time. For sports contexts or active sailing, polyamide NATO or FKM rubber are practical alternatives compatible with the Aqua Terra's technical character.

Obtain a spring bar tool. Position the watch in good light and secure it. Insert the flat end of the tool into the small lateral groove of one of the spring bars, pushing toward the case center to compress the internal spring. When you feel the pressure release, the old strap will detach. Repeat on the other side. To insert the new strap, align the ends with the lugs and use the spring bar tool again to compress the springs and seat the bars. Perform the operation gently to avoid scratching the case.

Yes. 20mm is a very common width in the quality aftermarket strap market. You will find straps in alligator, calf, shell cordovan, rubber, and NATO fabrics perfectly compatible. Milano Straps offers a wide selection of 20mm straps customizable in sizes, materials, colors, and stitching finishes. Always verify the reference before ordering to avoid incompatibilities.

Durability depends on the tanning method, type of leather, and intensity of use. A quality artisanal vegetable-tanned alligator or calf maintains functionality for 4-6 years with regular wear (5-7 days per week). A more delicate calf strap can last 3-5 years. Actual durability extends considerably if the watch is worn alternating with other timepieces. Critical factors are ambient humidity, prolonged direct sun exposure, and contact with salt sweat. An alligator strap develops a fascinating patina after 12-18 months of regular wear, increasing its aesthetic value with age.