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Bremont · Supermarine

Strap for Supermarine S301 Stainless Steel / Black / Calf

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 Bremont
Lug width20 mm
Case diameter40 mm
ReferenceS301/BK
FamilySupermarine
MovementBremont caliber BE-36AE hours, minutes, seconds | date, day | chronometer
Year2017
CaseStainless Steel

Spring bar

Swiss Standard universal spring bars

The right category for this model · 316L steel, all lug widths 13–26 mm

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Straps for the Supermarine S301/BK

Selected for the 20 mm lug width · workshop selection

All 20 mm straps →

The Supermarine S301/BK, seen from the bench

The Bremont Supermarine S301/BK is a 40 mm stainless steel instrument watch featuring the automatic Bremont BE-36AE chronometer-certified movement. The unidirectional bezel with defined clicks enables accurate timing even with gloves, while the anti-reflective sapphire crystal ensures readability in all light conditions. The 316L steel case develops a patina over time, and the transparent caseback displays the visible gearing. The 20 mm lug width maintains proper proportions between case diameter and strap width.

Frequently asked questions

What is the lug width of the Bremont Supermarine S301/BK?

The Bremont Supermarine S301/BK features 20-millimetre lugs (lug width). This specification falls outside the common mass-market standards of 18mm or 22mm, requiring bespoke strap construction to ensure precise fit without lateral play or tension.

Which strap material is recommended for the Supermarine S301/BK?

Alligator leather with vegetable tanning, English calf grain, or tactical NATO cotton-polyester are ideal for this chronometer-rated instrument. Coarse-grained leather balances the rigour of the stainless steel case. For aquatic or tactical deployments, FKM rubber delivers superior technical performance.

How do you accurately measure the lug width of a watch?

Use a digital calliper positioned perpendicularly across the interior of the lugs, measuring the spacing precisely. For the S301/BK, the reading must be 20mm. Inaccurate measurement compromises strap fit. Consult your Bremont documentation or contact the manufacturer directly to verify specifications.

Are aftermarket straps compatible with the Bremont Supermarine S301/BK?

Yes, provided they are manufactured to exact 20mm lug width specifications. Milano Straps' bespoke strap designs guarantee full compatibility without case modification. Precision in leather perforation and strap geometry ensures fit equivalent to OEM Bremont straps.

What is the typical lifespan of a leather strap on a Supermarine-class instrument?

A premium vegetable-tanned leather strap worn daily on the S301/BK typically lasts 3–5 years. Longevity depends on wear frequency, moisture exposure, and maintenance protocols. Alligator or shell cordovan straps may reach 7–10 years. Rotating multiple straps significantly extends individual strap lifespan.

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