Swatch · Sistem 51

Strap for Sistem Schwiiz

Takes 16 mm straps. Verified lug width, the straps that fit this model, and answers to the most common questions.

Lug width16 mm
Case diameter42 mm
ReferenceSUTB404
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

Straps for the Sistem 51 SUTB404

Selected for the 16 mm lug width · workshop selection

All 16 mm straps →

The Sistem 51 SUTB404, seen from the bench

The Swatch Sistem 51 SUTB404 features a 42 mm transparent plastic case with a 16 mm lug width, housing the Sistem51 mechanical caliber beating at 3 hertz with manual winding. This model represents a radical approach to contemporary watchmaking with 51 components assembled by machine, eliminating unnecessary decorations while maintaining Swiss precision standards. The transparent case allows direct observation of the caliber's movement, transforming the dial into a window to pure mechanics.

Frequently asked questions

What is the lug width of the Swatch Sistem 51 SUTB404?

The SUTB404 features a 16-millimetre lug width. This measurement is specific to this model and must be respected when selecting a replacement strap. To measure the lugs, position the ruler from one spring bar to the other internally, perpendicular to the line connecting the lugs of the case.

Which strap is most suitable for the Swatch Sistem 51 SUTB404?

The ideal strap depends on personal style. To emphasise the transparent case design, we recommend fine-grain alligator. For a classical approach, vegetable-tanned calf leather develops a beautiful patina over years. A NATO strap in cordura maintains the radical aesthetic coherence of the design. Vulcanised rubber underscores the functional pragmatism of the watch.

How do I change the strap on a Swatch Sistem 51 SUTB404?

The SUTB404 uses a spring bar fastening system. To change the strap, you must remove the spring bars from the case lugs using a dedicated tool or thin screwdriver. Insert the new strap by seating the passant rings onto the spring bars, then re-insert the bars. This operation requires care to avoid damaging the plastic case.

Can I use an aftermarket strap on this watch?

Yes, you can use replacement straps provided they respect the 16-millimetre lug width. It is important to verify that the spring bars are compatible with the plastic case. We recommend straps specifically manufactured for 16mm lugs to ensure precise fit and avoid structural tension on the case.

How long does a leather strap last on a Swatch Sistem 51?

A quality leather strap on a daily-worn watch maintains structural functionality for 3 to 5 years. Durability varies depending on the material (calf, alligator, shell cordovan react differently to moisture) and the environment of use. Vegetable-tanned leather develops patina and character over time, whilst rubber remains unchanged for longer periods.

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.

Request an appointment →

Casati Milano · Via XX Settembre 15, Milan · by appointment only