Strap for SUB 300T Whitepearl / Bracelet

The lug width of the Doxa SUB 300 840.10.011.10 is 20mm. This width is specific to the 42.50mm case and is non-negotiable: a strap of different dimensions will not fit correctly into the soldered lugs. It is essential to verify this measurement before purchasing any aftermarket strap.

The choice depends on your intended use. For daily elegance: an alligator or vegetable-tanned calf leather in dark brown or black. For underwater functionality: a black FKM rubber, resistant to chlorine and salt water. For historical authenticity: a navy blue fabric NATO. All must have a 20mm lug width to ensure perfect fit.

The strap is removed by extracting the spring bars (pins) from the lugs using a dedicated spring bar tool. The pins should be gently pulled downward: pushing horizontally will damage the internal spring. Once the lugs are free, the new 20mm strap is threaded through and the pins are reinserted until they click. We recommend having a professional watchmaker perform this operation to avoid scratches.

Any strap with a 20mm lug width is compatible with the 840.10.011.10. However, we recommend verifying leather thickness (maximum 4mm) and initial stiffness, especially with vegetable tanning. Atelier Casati Milano manually tests each pairing to exclude fit defects or conformity issues.

A quality vegetable-tanned calf leather strap lasts approximately 3-5 years with daily use, developing natural patina. Industrial-grade FKM rubber resists for 5-7 years before hardening. A fabric NATO lasts indefinitely, though it may felt over time. Regular maintenance (wax conditioning, post-immersion drying) significantly extends lifespan.