Rolex
Datejust 31 178344-0063— lug 16mm

The lug width of the Rolex Datejust 31 reference 178344-0063 is 16mm. This measurement is taken with a calliper between the two lugs on the case back, at the narrowest point of the lug gap. It should not be confused with the case diameter (31mm), nor with the lug width of the Datejust 36 (20mm) or the Datejust 28 (13mm). Any aftermarket strap must measure exactly 16mm at the attachment end to ensure correct fitment without play or stress on the lugs.

For the Datejust 31 in white gold and steel, alligator leather — either classic or hornback — is the most coherent choice given the formal register of the watch: the natural grain complements the cold lustre of white gold. Box-calf leather with vegetable tanning is the most versatile alternative, developing a patina over time. Shell cordovan offers a dense, almost mirror-like surface. For sporting or summer use, a shaped rubber strap preserves the Oyster water resistance. The ideal choice depends on the intended context and the dial colour palette.

Changing the strap on a Datejust 31 requires a spring bar tool (also called a lever tool) with a forked tip or a fine-tipped dedicated instrument. The spring bars measure 1.8mm in diameter and seat within the 16mm lugs. Compress the spring bar, extract it from the lug hole and remove the strap. The operation does not require opening the case and is fully reversible. To avoid scratching the white gold lugs, use a tool with a plastic or padded tip, or apply low-tack tape over the lug surfaces before working.

Yes, there is a wide range of aftermarket straps compatible with the Datejust 31 ref. 178344-0063. The essential requirement is a lug width of 16mm. Casati Milano and milanostraps.it offer handcrafted straps in alligator, calf leather, shell cordovan and rubber, produced specifically for this lug size. Total length can be customised to the wearer's wrist measurement. The standard buckle width is 14mm; a deployant clasp in steel or white gold PVD is also available for greater convenience and to reduce wear on the strap at the buckle area.

The lifespan of a leather strap depends on the quality of the tanning process, daily care and frequency of use. A high-grade alligator strap, kept away from prolonged water and perspiration exposure and treated periodically with a conditioning cream, typically lasts between three and five years with regular wear. Vegetable-tanned box-calf has a comparable lifespan but improves aesthetically as it develops a patina. Shell cordovan is notably durable owing to the density of its fibre structure. Casati Milano provides an 18-month warranty against manufacturing defects on all straps.