Rolex
Datejust 31 178240-0040— lug 16mm

The Rolex Datejust 31 ref. 178240-0040 has a lug width of 16mm. This measurement should be taken with a digital calliper positioned between the inner edges of the lugs, flush with the case. Respecting this dimension is essential to ensure a precise fit and correct aesthetic alignment of the strap.

For the stainless steel Datejust 31, alligator leather with a glossy finish or vegetable-tanned calfskin offer the best aesthetic balance. Glossy alligator contrasts elegantly with the brushed Oyster case, while calfskin develops a natural patina over time. For sport or aquatic use, a rubber strap with a butterfly deployant clasp is the most practical option. All straps must feature 16mm end pieces.

To replace the strap on the Datejust 31, you will need a fine-tipped springbar tool. The Datejust lugs accommodate standard spring bars: insert the tool tip into the lug hole, compress the spring bar and slide the strap free. Care must be taken to avoid scratching the case. If in doubt, it is advisable to consult a watchmaker or the Casati Milano atelier.

Yes. The Datejust 31 ref. 178240-0040 accepts any aftermarket strap with 16mm end pieces and standard spring bars. Milano Straps offers a curated selection of handcrafted 16mm straps in various materials — alligator, calfskin, shell cordovan, NATO and rubber — manufactured to precise millimetre tolerances for a perfect fit on the 31mm Oyster case.

The lifespan of a leather strap depends on the quality of the hide, the tanning method and daily use. A high-grade alligator or shell cordovan strap, properly maintained and kept away from prolonged water exposure and excessive perspiration, can last between 3 and 7 years. Vegetable-tanned calfskin typically lasts 2 to 4 years. Milano Straps provides an 18-month warranty against manufacturing defects on all straps.