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Swatch · Sistem 51

Strap for Swatch Sistem 51 SUTN403

The Sistem Sea takes 16 mm straps. Verified lug width, the straps that fit this model, and answers to the most common questions.

Lug width

16mm
16 mm strapsAll Swatch
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Lug width16 mm
Case diameter42 mm
ReferenceSUTN403
FamilySistem 51
MovementSwatch caliber Sistem51 Date
Year2017
CasePlastic

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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What I'm asked about the Swatch Sistem 51 SUTN403

What strap size does the Swatch Sistem 51 SUTN403 take?

The Swatch Sistem 51 SUTN403 needs 16 mm between the lugs, usually 14 mm at the buckle. It's the size I've been fitting on it for years.

Can the strap on the Swatch Sistem 51 SUTN403 be changed?

Yes. It has spring bars between the lugs: with the right tool the strap comes off in a minute. If you'd rather not risk a scratch, I do it in the workshop.

Can I put a leather strap on the Swatch Sistem 51 SUTN403?

Yes, in 16 mm leather. On a 42 mm case a calf strap works every day; if you want something more, alligator.

Which strap do you recommend for the Swatch Sistem 51 SUTN403?

A 16 mm calf strap, for every day. You'll find it ready in the 16 mm collection. If you'd rather have something built on your wrist, the Casati atelier.

Straps for the Sistem 51 SUTN403

Selected for the 16 mm lug width · workshop selection

All 16 mm straps →

The Sistem 51 SUTN403, seen from the bench

The Swatch Sistem 51 Sea is a mechanical automatic watch launched in 2013 with 51 components assembled by robots. The case measures 42 mm in diameter and is crafted from polycarbonate for durability and lightweight construction. The Swatch caliber Sistem51 automatic movement beats at 3 hertz with over 90 hours of power reserve. The watch features a 16 mm lug width, which is the precise measurement required for compatible straps to ensure proper fit without lateral play or tension.

Frequently asked questions

Which strap is best suited for the Swatch Sistem 51 SUTN403?

The choice depends on intended use and aesthetic preference. A leather strap with vegetable tanning develops patina over time; an alligator model elevates sophistication; NATO straps offer sportiness and easy changeability; FKM rubber ensures durability and full water resistance. All must feature a 16mm lug width.

Are aftermarket straps compatible with the Swatch Sistem 51 SUTN403?

Yes, provided they conform to the 16-millimetre lug width. Artisanal straps constructed to mechanical standards integrate seamlessly. It is advisable to confirm compatibility with the supplier and verify that the strap features the correct attachments for the SUTN403's lugs.

How long does a leather strap last on the Sistem 51 SUTN403?

A quality leather strap with vegetable tanning typically lasts 5–8 years with regular wear. Longevity depends on frequency of use, climate conditions, and maintenance practices. The patina that develops naturally is not deterioration, but aesthetic ageing. NATO and rubber straps have superior lifespans (10+ years).

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

The atelier's website: casatimilano.com