Strap for Seamaster Planet Ocean 600M Co-Axial 43.5 Master Chronometer Stainless Steel / White / NATO

The lug width of the Omega Seamaster Planet Ocean 215.32.44.21.04.001 is 21 millimetres. This is the distance between the two metal lugs on the case where the strap is attached. Measuring it correctly is essential to ensure a precise fit without slipping or binding.

The choice depends on your intended use and desired aesthetic. For formal occasions, smoke grey alligator or vegetable-tanned calf creates elegance without competing with the dial. For sports versatility, vulcanised rubber remains unmatched thanks to its resistance to salt water and chlorine. A cognac brown calf with natural patina is ideal if you desire a finish that reflects your wearing time.

The replacement requires a specific tool called a spring bar tool. Position the watch with the case facing upwards, locate the end of the metal shoulder spring, and with the tool (a thin rod with one or two points) gently compress the spring towards the centre of the case. Once compressed, the old strap slides out. Insert the new one by aligning the lug hole with the spring pin, and release. Repeat for the opposite lug.

Yes, provided it has been specifically made with a 21mm lug width. Quality aftermarket straps, such as those in alligator, calf, or rubber available from Milano Straps, are fully compatible and often offer a superior colour variety compared to OEM straps. It is important to always verify that the lug width is exact to avoid play or abnormal pressure.

Durability varies depending on the material, use, and environmental conditions. Vegetable-tanned calf typically lasts 3–5 years with daily wear, developing a patina over time that increases its character. Alligator, thanks to its skin structure, tends to remain more rigid and can last 4–6 years. Factors such as direct sun exposure, humidity, and perspiration accelerate ageing. Vulcanised rubber, if not exposed to intense UV rays, maintains its elastic properties for 6–8 years. Casati Milano provides an 18-month warranty on all custom-made straps.