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Rolex · Day-Date 36

Strap for Day-Date 36 White Gold / Fluted / Opal-Diamond / President

Takes 20 mm straps. Verified lug width, the straps that fit this model, and answers to the most common questions.

Lug width

20mm
20 mm strapsAll Rolex
Lug width20 mm
Case diameter36 mm
Reference128239-0021
FamilyDay-Date 36
MovementRolex caliber 3255 Hours, Minutes, Seconds | Date, Day | Chronometer
CaseWhite Gold

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Straps for the Day-Date 36 128239-0021

Selected for the 20 mm lug width · workshop selection

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The Day-Date 36 128239-0021, seen from the bench

The Rolex Day-Date 36 in 18-karat white gold, reference 128239-0021, represents the contemporary evolution of an iconic timepiece launched in 1956 as the world's first automatic weekly calendar watch. The 36 mm case houses the COSC-certified caliber 3255 with Chronergy escapement and Parachrom Blue hairspring, delivering precision of −2/+2 seconds per day and 70-hour power reserve. The white gold case features a screw-down caseback and 100 m water resistance, with a fixed white gold bezel and Champagne or Slate dial options. The 20 mm lug width accommodates leather straps with 3.8–4.2 mm thickness for a secure, proportionate fit.

Frequently asked questions

What is the lug width of the Rolex Day-Date 36 128239-0021?

The lug width of the Day-Date 36 white gold reference 128239-0021 is 20 millimetres. This measurement denotes the horizontal distance between the two lugs (horns) of the case where the strap inserts. A compatible strap must have a thickness between 3.8 and 4.2 millimetres to sit without lateral play.

Which strap material is most suitable for the Day-Date 36 in white gold?

Alligator remains the traditional pairing with white gold, owing to its fine grain and patina that develops with natural elegance. Alternatively, vegetable-tanned calf leather offers tactile robustness and visible grain. For less formal wear, NATO fabric straps with leather keepers provide aesthetic versatility and daily practicality.

How do you change the strap on a Rolex Day-Date 36?

Strap replacement requires a dedicated tool (spring bar tool) or a thin-bladed screwdriver. Insert the tool into the lugs to depress the elastic pins and leverage the strap away. We recommend entrusting this task to a professional watchmaker or Casati Milano's service to avoid case damage.

Is a non-original aftermarket strap compatible with the 128239-0021?

Yes, any strap with a 20-millimetre lug width is mechanically compatible. However, construction quality, durability, and aesthetic coherence depend on the manufacturer. Casati Milano's handcrafted straps respect Rolex original parameters whilst offering bespoke personalisation and curated materials.

How long does a leather strap last on a daily-wear wristwatch?

The lifespan of a leather strap depends on the tanning process, usage, and maintenance. High-quality alligator or vegetable-tanned calf lasts between 4 and 7 years with daily wear. The patina that develops is part of its authenticity. Casati Milano straps include an 18-month warranty against manufacturing defects and are renewable upon request.

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