Rolex
Datejust 31 178240-0033— lug 16mm

The Rolex Datejust 31 reference 178240-0033 features a lug width of 16 millimetres. This measurement is the distance between the case lugs (springbar attachement points) and is critical for selecting a compatible strap. To verify, insert a digital calliper or ruler between the internal lugs: you will measure exactly 16mm. Any strap designed for 16mm lug width will fit this model perfectly.

For the Datejust 31 178240-0033 in steel, we recommend three options. Alligator leather (distinctive rectangular scale pattern) is the classic choice, developing a natural patina over time. Shell cordovan—vegetable-tanned horsehide from the rump—offers exceptional durability and develops a characteristic sheen. Vegetable-tanned calf is the most versatile, available in colours ranging from light brown to deep black. All three materials maintain the sophisticated character of the steel case without competing visually with the dial.

Changing the strap on a Datejust 31 requires a spring bar tool. Position the watch with lugs facing upward. Insert the flat end of the spring bar tool into the small hole on one lug to decompress the internal spring, then withdraw the spring bar from the old strap. Repeat for the opposite lug. To install the new strap, align the spring bar ends and press inward until you hear a definitive click. Never force; the tool performs the work. If you lack experience, Casati Milano specialists can handle the installation professionally.

Yes, without reservation. Any strap manufactured for 16mm lug width is mechanically compatible with the Datejust 31 178240-0033. Artisanal straps in alligator, shell cordovan, or vegetable-tanned calf offer construction quality and personalisation options impossible with original Rolex straps. Milano Straps features a dedicated collection of 16mm-compatible straps, allowing you to select leather type, thickness, colour, and finishing according to your wrist and personal style. Many Rolex collectors prefer bespoke straps for variety and character.

A leather strap's lifespan depends on daily use, climate, and tanning quality. An artisanal strap in alligator or shell cordovan typically lasts 3–5 years with regular wear. Vegetable-tanned calf, being more delicate, ranges from 2–4 years. Factors such as perspiration, sun exposure, and moisture accelerate deterioration. To extend strap longevity, rotate with alternative straps, clean the leather with a soft cloth, and handle buckles and passant loops carefully. Casati Milano straps include an 18-month warranty against manufacturing defects, not normal wear.