Swatch · Sistem 51

Strap for Sistem Arlequin

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
ReferenceSUTW402
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 SUTW402

Selected for the 20 mm lug width · workshop selection

All 20 mm straps →

The Sistem 51 SUTW402, seen from the bench

The Sistem 51 was introduced by Swatch in 2013 as the first automatic mechanical movement composed of just 51 components assembled entirely by machines. The Sistem51 caliber offers a power reserve of 90 hours and includes the date function. The case features standard Swatch dimensions with a fully sealed construction.

Frequently asked questions

What is the exact lug width of the Swatch Sistem 51 SUTW402?

The lug width of the Swatch Sistem 51 SUTW402 is 20 millimetres. This measurement is determined by the case structure and represents the internal space between the lugs where the watch strap bars are inserted. Any aftermarket strap for this model must have exactly 20mm width to guarantee perfect compatibility and security during use.

What is the best strap to pair with the Swatch Sistem 51 SUTW402?

The best strap depends on intended use and personal preferences. For an elegant aesthetic upgrade, we recommend alligator or calf leather with vegetable tanning, which creates a fascinating contrast with the transparent polymer case. For daily sporting use, a NATO strap in technical fabric maintains the casual spirit of the Sistem51. For high-wear environments, FKM rubber guarantees absolute durability. The key is always selecting artisanal quality materials that respect the compact proportions of the watch.

How do you change the strap on the Swatch Sistem 51 SUTW402?

Strap change is performed using a spring bar remover or small flat screwdriver. Position the tool under the spring bar connecting the strap to the case, applying pressure inward to release the internal spring. Once the spring retracts, the bar slides out easily. Repeat on the other side. To insert the new strap, align the lug ends with the case holes, position the spring bar and press until you feel the spring lock click into place. This procedure takes minutes and requires no special expertise.

Which aftermarket straps are compatible with the SUTW402?

All straps with a 20mm lug width are compatible with the Swatch Sistem 51 SUTW402. This includes quality leather options (calf, alligator, shell cordovan), NATO straps in fabric, FKM rubber straps, sports elastics, and even mid-range synthetic straps. Always verify the exact lug width before purchase. Milano Straps offers a complete catalogue of artisanal 20mm options, selected for construction quality and compatibility certified with this model.

How long does a leather strap last on the Swatch Sistem 51 SUTW402?

Leather strap durability depends on material quality, daily use and maintenance. A quality vegetable-tanned leather strap, worn under normal conditions, lasts between 18 and 36 months. The leather develops a natural patina that increases appeal over time. Shell cordovan is particularly resistant and can last over 4 years. To extend durability, protect the strap from prolonged moisture and rotate it with other solutions if wearing the watch daily. Periodic maintenance with leather-specific creams restores elasticity and prevents cracking.

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