Strap for Sistem Frog

The lug width of the Swatch Sistem 51 SUTG401 is 20 millimetres. This measurement must be taken on the inside of the lugs, from outer edge to outer edge, to ensure correct strap compatibility. Do not confuse lug width with case thickness.

For the Sistem 51 SUTG401, we recommend a vegetable-tanned calf leather strap or a reversible polyester NATO strap. Vegetable-tanned leather develops a natural patina that enhances artisanal aesthetics, whilst NATO offers versatility and moisture resistance. In humid environments, an FKM rubber strap provides superior durability.

Strap change on the SUTG401 is performed via the spring bars inside the lugs. Use a spring bar tool to gently push the elastic pin inward into the case, releasing the lug. Insert the new 20mm strap by aligning the lug to the entry holes, then click the elastic pin until fully engaged.

Yes, provided it measures exactly 20 millimetres. However, we recommend straps specifically designed for 42mm watches, as this case size requires precise proportions between strap thickness and case mass. Artisanal quality straps guarantee uniform weight distribution and greater durability over time.

A quality vegetable-tanned leather strap can last 3–5 years with daily use, provided regular maintenance: monthly cleaning, air-drying if wet, and periodic application of natural balm. Visible ageing of the patina does not represent deterioration, but aesthetic evolution that increases the narrative value of the accessory.