Rolex · Datejust 31

Strap for Datejust 31 Rolesor Yellow Diamond / Jubilee / Steel Roman

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
Reference178383-0040
FamilyDatejust 31
MovementRolex caliber 2235 hours, minutes, seconds | date | chronometer
CaseYellow Gold, Stainless Steel

Spring bar

Spring bars for Rolex

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

Straps for the Datejust 31 178383-0040

Selected for the 16 mm lug width

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The Datejust 31 178383-0040, seen from the bench

The Rolex Datejust 31 reference 178383-0040 belongs to one of watchmaking's most iconic lineages, introduced in 1945 as the first wristwatch with a date window at 3 o'clock. This 31mm mid-size version in yellow Rolesor—a combination of Oystersteel and 18-carat yellow gold—features the automatic Rolex caliber 2235 movement, COSC-certified chronometer with -2/+2 seconds per day precision. The Oyster case with yellow gold bezel, sapphire crystal with anti-reflective treatment, and screw-down Twinlock crown provides 100 meters water resistance. The 16mm lug width is exclusive to this Datejust 31 family and requires curved or semi-curved strap terminations to fit properly.

Frequently asked questions

What is the lug width of the Rolex Datejust 31 178383-0040?

The Rolex Datejust 31 reference 178383-0040 has a lug width of 16mm. This measurement is taken with a calliper across the inner distance between the two parallel lugs and is the nominal dimension to specify when purchasing a compatible replacement strap.

What is the best strap for the Rolex Datejust 31 178383-0040?

For the Datejust 31 in yellow Rolesor, a vegetable-tanned alligator strap in cognac or midnight blue tones is the most coherent choice given the watch's character. The scaled grain of alligator leather complements the refinement of the yellow gold bezel. For more active use, a rubber or technical NATO strap offers comfort and water resistance.

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

To replace the strap on the Datejust 31, the spring bars connecting the strap to the case lugs must be removed. Use a fine-tipped springbar tool, inserting it into the dedicated slot on the side of the spring bar and compressing to release. Work on a soft surface to avoid scratching the case, and ensure the new spring bars are 16mm in length with a curved end profile suited to the Datejust's lug geometry.

Are there aftermarket straps compatible with the Rolex Datejust 31 178383-0040?

Yes. The aftermarket offers numerous straps for the 16mm lug width compatible with the Datejust 31. Milano Straps provides handcrafted options in alligator, calf leather, shell cordovan and nylon, selected for correct dimensions and curved end profiles. It is important to verify that the strap has curved or semi-curved ends to fit correctly against the Oyster case geometry.

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

The lifespan of a leather strap depends on leather quality, frequency of use and maintenance. A high-quality vegetable-tanned alligator strap, rotated regularly and stored away from moisture and direct UV exposure, can last between three and seven years while retaining a dignified appearance. Periodic application of a neutral leather conditioner significantly extends strap life. Milano Straps offers an 18-month warranty against manufacturing defects.

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