Rolex
Datejust 31 178384-0055— lug 16mm

The Rolex Datejust 31 ref. 178384-0055 has a lug width of 16mm. This measurement should be taken with a calliper between the inner edges of the two lugs on the case back. It is essential not to confuse this with the 20mm lug width of larger Datejust references, as straps are not interchangeable without adaptors.

For the two-tone steel and white gold case of the ref. 178384-0055, flat-belly alligator or vegetable-tanned calf leather straps offer the best balance of elegance and aesthetic coherence. Alligator enhances the formality of the fluted bezel; vegetable-tanned calf develops a patina over time for a more personal result. Rubber is recommended for sporting or summer use.

To replace the strap on the Datejust 31, a double-ended spring bar tool is required to remove the spring bars from the lugs. Care must be taken to avoid scratching the case: a plastic or rubber cushion placed against the lug is recommended during removal. The original spring bars have a diameter of 1.5mm and can be reused with a new strap if they remain in good condition.

Yes, several artisan manufacturers — including Casati Milano through milanostraps.it — produce aftermarket straps with a 16mm lug width compatible with the Datejust 31 ref. 178384-0055. It is important to confirm that the strap is built specifically for 16mm rather than adapted from a different size, in order to ensure a precise fit without lateral play at the lugs.

Longevity depends on the material and usage. A quality alligator strap, properly cared for (kept away from prolonged moisture and perfumes), typically lasts 3–5 years with regular wear. Vegetable-tanned calf has a similar lifespan but develops a characteristic patina over time. Shell cordovan is the most durable of the premium leathers and can exceed 5 years while retaining structural integrity. Casati Milano offers an 18-month guarantee against manufacturing defects.