Strap for Speedmaster Professional Moonwatch

The lug width is 20mm. This dimension is specific to the 3870.50.31 model and is compatible with all standard 20mm straps. It is measured by placing the watch on a table and measuring the internal distance between the two lugs of the case: the value will be exactly 20mm.

It depends on use and aesthetic preferences. For classic elegance, brown or black alligator; for durability and mirror patina, shell cordovan; for softness and versatility, vegetable-tanned calf. For sports or hiking use, NATO strap or vulcanized rubber. All materials are available in 20mm.

The change is simple: use a dedicated tool (spring bar tool) or a rounded toothpick. Insert the tool into the small lateral opening under the lug, push toward the center to release the anchor spring, remove the old strap. Position the new strap by aligning it vertically, push until the spring clicks into place. Repeat on the other side.

Yes. The 3870.50.31 uses the 20mm standard, so any 20mm strap (alligator, calf, shell cordovan, NATO, rubber) is physically compatible. Quality and durability depend on the manufacturer: milanostraps offers handcrafted straps with 18-month warranty if created by the Casati Milano atelier.

A quality alligator or calf strap, with regular maintenance (monthly cleaning, drying after humidity), lasts 3-4 years. Shell cordovan, being more resistant, easily reaches 5-7 years. Vulcanized rubber has similar lifespan (5-7 years) and requires no maintenance. The patina of premium leather does not indicate deterioration but aesthetic enrichment over time.