Rolex
Datejust 31 178341-0009— lug 16mm

The Rolex Datejust 31 reference 178341-0009 has a lug width of 16mm. This measurement is specific to the 31mm diameter variant and is taken as the internal distance between the two case lugs at the strap attachment point. Only straps with a 16mm fitting should be used to ensure a correct, play-free installation.

For the Datejust 31 178341-0009, with its two-tone steel and Everose case, the most appropriate materials are: polished alligator belly in bordeaux or midnight blue for formal settings, shell cordovan in cognac or dark brown for a more personal character with an evolving patina, and vegetable-tanned calfskin for daily wear. A brushed steel deployant clasp is the most coherent closure choice for this two-tone reference.

To replace the strap on the Datejust 31 178341-0009, the spring bars connecting the strap to the case lugs must be removed. A fine-tipped springbar tool is inserted into the side hole of the lug and used to compress the bar. Care must be taken to avoid scratching the Everose gold case. Alternatively, Atelier Casati Milano can perform the replacement on-site by appointment.

Yes. The aftermarket offers high-quality straps with a 16mm fitting compatible with the Datejust 31 178341-0009. Milano Straps produces handcrafted straps in alligator, shell cordovan and vegetable-tanned calfskin, fitted with standard 16mm spring bars. It is important to verify that the strap end profile — curved or straight — matches the lug geometry of the case for a precise fit.

The lifespan of a leather strap on a Datejust 31 depends on the material and frequency of use. A quality alligator strap, rotated regularly and kept away from water and excessive perspiration, typically lasts 2–4 years. Shell cordovan, being denser and more compact, can exceed 5 years. Milano Straps products are covered by an 18-month warranty against manufacturing defects.