Strap for Seamaster Master Co-Axial 39.5 London Edition Stainless Steel / Blue / Alligator

The lug width of the Omega Seamaster 511.13.40.20.03.001 City Edition is 20 mm. This measurement represents the space between the attachment pins on the case. It is important to verify it with a digital caliper before purchasing a compatible strap, as small tolerances (19.8–20.2 mm) are acceptable, but different widths would cause instability on the wrist.

The ideal pairing depends on the intended use. For formal and professional contexts, we recommend alligator in dark shades (black, havana) or natural shell cordovan. For casual-sporty style, vegetable-tanned calf in brown or beige, or butyl rubber for water activities. The custom handcrafted strap from Casati Milano allows you to choose the leather, color, and finish ideal for your personal style.

Changing the strap requires a spring bar tool. Position the watch on a soft surface, gently insert the flat tip of the tool into the slot of the attachment pin, lift until the spring bar appears, then remove the old strap. Insert the new strap by aligning it correctly and allow the spring bar to reposition itself. If you prefer to avoid any risk, Omega service centers or specialized craftsmen (such as Casati Milano) perform this change free of charge with the purchase of a strap.

All straps with a 20 mm lug width are compatible with the Seamaster 511.13.40.20.03.001. MilanoStraps offers a curated collection of 20mm straps in alligator, Italian leather, shell cordovan, and rubber, customizable in length, color, and stitching thread. Compatibility verification is simple: measuring the space between the pins on the case should be 20 mm.

The durability of a quality leather strap depends on daily use and care. An alligator or cordovan strap of artisanal manufacture lasts 3–5 years with regular use, developing a natural patina that enhances its appeal. Vegetable-tanned calf offers similar durability but with a texture that changes more visibly. Casati Milano offers an 18-month warranty on all straps produced, ensuring quality and durability over time.