Rolex
Datejust 31 278240-0008— lug 16mm

The Rolex Datejust 31 reference 278240-0008 has a lug width of 16mm. This measurement refers to the internal distance between the two lugs of the case, taken with a digital calliper perpendicular to the longitudinal axis of the watch. Respecting this dimension is essential for a correct fit of any aftermarket strap.

For the stainless steel Datejust 31, the most suitable straps are vegetable-tanned alligator for formal settings, smooth calf leather for everyday wear, shell cordovan for a compact and long-lasting surface, and FKM rubber for sport use. The choice should also consider the dial colour: with blue or sunburst dials, dark brown or navy leather offers the most coherent chromatic pairing.

To replace the strap on a Datejust 31, you will need a dual-tip spring bar tool with a 0.8mm or 1.0mm fork. The spring bars are compressed laterally within the lugs and carefully extracted with gentle leverage. It is advisable to work on a soft pad to avoid scratching the polished case surfaces. Alternatively, authorised retailers and specialist ateliers can perform the swap without risk.

Yes. The aftermarket offers a wide range of 16mm straps compatible with the Datejust 31. Artisan manufacturers such as Casati Milano produce bespoke straps in alligator, calf, and shell cordovan leathers, with standard 1.5mm spring bars that fit the lugs of the 278240-0008 precisely. It is important to confirm that the attachment width is exactly 16mm and that the ends are curved to follow the case profile.

The lifespan of a leather strap depends on the quality of the hide, the tanning method, and daily usage. A high-quality vegetable-tanned alligator strap, properly maintained — avoiding prolonged exposure to water and perspiration, and conditioned every three to four months — typically lasts between three and six years. Using a folding deployant clasp instead of a pin buckle significantly reduces mechanical stress on the strap and extends its service life.