Omega · Seamaster 120M

Strap for Seamaster 120M Multifunction Stainless Steel / Blue

Takes 18 mm straps. Verified lug width, the straps that fit this model, and answers to the most common questions.

Lug width18 mm
Case diameter37 mm
Reference2521.81.00
FamilySeamaster 120M
MovementOmega caliber 1665 Hours, Minutes, Small Seconds, Additional 24 Hour Hand (adjustable) | Date, Month, Perpetual Calendar, Year Indicator | Chronograph, Countdown, Flyback, Foudroyante, Rattrapante | Alarm
CaseStainless Steel

Recommended spring bar

Spring bars Omega 18mm — single diameter

Technical match for lug width and diameter · lug 18 mm · Ø 1.8 mm

All Omega spring barsOpen →

The Seamaster 120M 2521.81.00, seen from the bench

The Seamaster 120M reference 2521.81.00 is equipped with the Omega 1665 caliber featuring chronograph, perpetual calendar and adjustable 24-hour GMT hand functions. The watch offers advanced complications including flyback, rattrapante and foudroyante, as well as countdown function and date, month and year indicators. 18mm lugs complete the technical specifications of the model.

Frequently asked questions

What is the correct lug width for the Omega Seamaster 120M 2521.81.00?

The lug width is 18 mm on both sides. This measurement is specific to mid-size Seamaster models from the 1970s. You can verify it by placing a ruler on the inner surface of the lug, in the narrowest area where the strap makes contact, excluding the lateral shoulders.

Which strap type pairs best with the Omega Seamaster 120M 2521.81.00?

Vegetable-tanned alligator represents the most fitting choice: medium grain, patina that evolves over time. Shell cordovan suits equally well for durability and natural lustre. Alternatively, FKM rubber for direct sports use, or ballistic NATO for resonance with the watch's technical heritage.

How do you change the strap on an Omega Seamaster 120M without damaging the case?

The change requires minimal tools: a small flat-blade screwdriver, preferably with rounded tip, and a case holder that stabilizes the watch without scratching. Insert the screwdriver into the small lateral slot of the pin that secures the strap to the lug, and release the pin outward with controlled movement. Proceed the same way on the opposite lug.

Is an aftermarket strap of good quality compatible with the 2521.81.00?

Yes, provided that the lug width is exactly 18 mm. Many modern standardized straps (20 mm or 16 mm) will not fit correctly. On milanostraps.it you will find artisanal straps designed specifically for this measurement, with construction finishes that respect the original Omega proportions.

How long does a leather strap last on a watch like the Seamaster 120M?

A high-quality alligator or cordovan strap, subject to ordinary maintenance (occasional cleaning, drying after water contact), maintains structural and aesthetic integrity for 5-7 years with regular use. FKM rubber typically lasts 4-6 years before losing elasticity. Lifespan also depends on the intensity of sun exposure, humidity, and temperature fluctuations.

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