Rolex · Datejust 31

Strap for Datejust 31 Stainless Steel Domed / Oyster / Dark Rhodium Floral

Takes 16 mm straps. Verified lug width, the straps that fit this model, and answers to the most common questions.

Lug width16 mm
Case diameter31 mm
Reference178240-0040
FamilyDatejust 31
MovementRolex caliber 2235 hours, minutes, seconds | date | chronometer
CaseStainless Steel

Spring bar

Spring bars for Rolex

The right category for this model · choose the 16 mm size

Straps for the Datejust 31 178240-0040

Selected for the 16 mm lug width

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The Datejust 31 178240-0040, seen from the bench

The Datejust 31 reference 178240-0040 is equipped with the automatic caliber 2235 with hour, minute, second and date functions. The 31mm case is fitted with 16mm lugs and a certified chronometer movement. It represents the feminine version of the Rolex Datejust collection.

Frequently asked questions

What is the lug width of the Rolex Datejust 31 ref. 178240-0040?

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.

What is the best strap for the Rolex Datejust 31 178240-0040?

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.

How do you change the strap on a Rolex Datejust 31?

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.

Are there aftermarket straps compatible with the Rolex Datejust 31 178240-0040?

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.

How long does a leather strap last on a Rolex Datejust 31?

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.

The next step

The right strap isn't chosen. It is built, together.

From the atelier appointment to delivery, every step is made for those who know that things done well take time. Rare leathers, one piece at a time, eighteen months of warranty.

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Casati Milano · Via XX Settembre 15, Milan · by appointment only