Strap for Seamaster Aqua Terra 150M Master Co-Axial 38.5 Stainless Steel / Red Gold / Silver

The lug width of the 231.23.39.21.02.001 model is 18mm. This dimension is the space between the case lugs where the strap attaches. To verify it, measure the distance between the centers of the two horizontal lugs on the case: it must be exactly 18mm. A strap of a different size will not fit correctly and would cause instability during use.

For this two-tone red gold and steel model, we recommend alligator in dark shades (brown, black, blue) for a classic approach, or vegetable-tanned calf with developed patina for a more personal narrative. Bordeaux shell cordovan creates a contemporary contrast with the red gold. For legitimate sports use, FKM rubber or NATO in black/gray maintain elegance while preserving water resistance.

The Aqua Terra strap is changed by removing the spring bars (lugs): with the watch face down, use a dedicated tool (spring bar tool) to compress the internal spring of the lug and extract it from the case. Then insert the new strap by threading the spring bar into the lug seat. This is a delicate operation: if you are not experienced, entrust it to a watchmaker or professional strap change service.

Yes, any artisanal strap with 18mm lug width is compatible with the 231.23.39.21.02.001, provided the spring bars are the correct length (typically 20-22mm for this case). Verify the exact dimensions with the seller before purchasing. The straps offered on milanostraps.it are tested and guaranteed compatible.

A high-quality artisanal leather strap (alligator, calf, shell cordovan) typically lasts 3-5 years with regular daily use, depending on the frequency of water contact and sun exposure. Vegetable-tanned calf, developing patina, can prove more emotionally durable even if visibly worn. Casati Milano offers an 18-month warranty on all bespoke straps, covering manufacturing defects.