Rolex
Datejust 31 178383-0040— lug 16mm

The Rolex Datejust 31 reference 178383-0040 has a lug width of 16mm. This measurement is taken with a calliper across the inner distance between the two parallel lugs and is the nominal dimension to specify when purchasing a compatible replacement strap.

For the Datejust 31 in yellow Rolesor, a vegetable-tanned alligator strap in cognac or midnight blue tones is the most coherent choice given the watch's character. The scaled grain of alligator leather complements the refinement of the yellow gold bezel. For more active use, a rubber or technical NATO strap offers comfort and water resistance.

To replace the strap on the Datejust 31, the spring bars connecting the strap to the case lugs must be removed. Use a fine-tipped springbar tool, inserting it into the dedicated slot on the side of the spring bar and compressing to release. Work on a soft surface to avoid scratching the case, and ensure the new spring bars are 16mm in length with a curved end profile suited to the Datejust's lug geometry.

Yes. The aftermarket offers numerous straps for the 16mm lug width compatible with the Datejust 31. Milano Straps provides handcrafted options in alligator, calf leather, shell cordovan and nylon, selected for correct dimensions and curved end profiles. It is important to verify that the strap has curved or semi-curved ends to fit correctly against the Oyster case geometry.

The lifespan of a leather strap depends on leather quality, frequency of use and maintenance. A high-quality vegetable-tanned alligator strap, rotated regularly and stored away from moisture and direct UV exposure, can last between three and seven years while retaining a dignified appearance. Periodic application of a neutral leather conditioner significantly extends strap life. Milano Straps offers an 18-month warranty against manufacturing defects.