Swatch
Sistem 51 SUTW404— lug 20mm

The SUTW404 features a fixed lug width of 20 millimetres. This is the orthogonal distance between the two spring bars that anchor the strap to the case. This specification is non-negotiable, so any aftermarket strap must be specifically manufactured for this width to ensure a secure fit without gaps.

The choice depends on usage and aesthetic preference. For a sartorial look, an alligator strap with vegetable tanning or vegetable-tanned calf leather is recommended, as it elevates the simplicity of the transparent case. For a sporty-casual aesthetic, a NATO strap in cotton or nylon is practical and economical. For humid or aquatic environments, a fluoroelastomer rubber strap offers durability without deterioration risk.

Changing the strap requires a dedicated tool called a spring bar tool. Position the tool's tip under the spring bar from beneath the case, applying gentle upward pressure to release the current strap. Repeat with the second bar. Insert the new strap's spring bars into the lugs and click them firmly into place until fully secured. If uncertain, consult a professional to avoid damage to the plastic case.

Yes, provided the strap explicitly bears a '20mm' marking or is SUTW-compatible. However, construction quality varies significantly: budget straps may exhibit gaps between case and band, undesired movement, or accidental unclasping. We recommend verified quality artisanal straps, where manufacturing tolerances are tighter and more reliable.

A quality leather strap—alligator, vegetable-tanned calf—typically lasts 3 to 5 years with daily use and ordinary care. Longevity depends on exposure to moisture, perspiration, direct sunlight, and cleaning frequency. A strap subjected to frequent wetting without drying deteriorates faster. The patina that develops over time is normal and desirable; the strap should not be considered exhausted until it exhibits structural tears or separation.