Swatch · Sistem 51

Strap for Sistem Gentleman

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

Lug width20 mm
Case diameter42 mm
ReferenceSUTF400
FamilySistem 51
MovementSwatch caliber Sistem51 date
Year2016
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 SUTF400

Selected for the 20 mm lug width · workshop selection

All 20 mm straps →

The Sistem 51 SUTF400, seen from the bench

The Sistem 51 was launched by Swatch in 2013 as the first automatic movement completely assembled by machines. It features the Sistem51 automatic caliber with date indication, composed of 51 components and equipped with a 90-hour power reserve. The plastic case has a diameter of 42mm with a transparent caseback that shows the central rotor.

Frequently asked questions

What is the lug width of the Swatch Sistem 51 SUTF400?

The Swatch Sistem 51 SUTF400 features a lug width of 20 millimetres. This measurement is the international standard for mid-to-large sized sports watches and is compatible with a wide range of aftermarket straps in leather, fabric, and rubber available in the market.

Which strap is best suited for the Swatch Sistem 51 SUTF400?

For the SUTF400, we recommend straps in textured calf leather or alligator with vegetable tanning, which create elegant contrast with the case's transparency. For sports use, NATO or vulcanised rubber straps are ideal. Your choice depends on context: premium leather for business environments, fabric or rubber for dynamic activities.

How do I change the strap on the Swatch Sistem 51 SUTF400?

Changing the strap on the SUTF400 is performed by removing the lateral lugs. Use a non-invasive tool (strap removal card or dedicated punch) to gently lift the locking pins on the case shoulders. The procedure is straightforward and requires no specialised skills. We recommend executing it carefully to avoid damaging the transparent polymer.

Is an aftermarket strap compatible with the Swatch Sistem 51 SUTF400?

Yes, any strap with a 20mm lug width is compatible with the SUTF400. Before purchase, verify that the supplier certifies exactly 20 millimetre width. At Milano Straps you'll find a selection of verified straps for this measurement, ready for installation without modifications.

How long does a leather strap last on the Swatch Sistem 51 SUTF400?

Durability depends on leather quality, frequency of use, and environmental conditions. A vegetable-tanned leather strap of good quality offers average durability of 18–36 months with regular wear. It develops natural patina over time, adding aesthetic character. Regular maintenance (occasional cleaning and conditioning) significantly extends longevity.

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