Sinn
Instrument Chronographs 103Classic— lug 20mm

The lug width of the Sinn 103 Classic is 20mm. This is the precise measurement between the two attachment pins on the case lugs. To verify, measure directly between the attachments: the value must correspond to 20mm to ensure compatibility with any aftermarket strap.

The choice depends on your use case. For elegant daily wear: vegetable-tanned leather or alligator. For humid or operational environments: vulcanised rubber with textured finish. For versatility and historical authenticity: rigid quality NATO fabric. All materials are available in 20mm width and provide secure grip and durability.

Remove the spring bar pins using a dedicated spring bar tool (small forked extractor). Position the tool under the first pin, apply gentle downward and lateral pressure until it releases from the seat. Repeat for the second pin. Insert the new strap, aligning the holes with the pins, and press firmly until you hear a click. Always verify security before wearing.

Yes, provided the strap is certified for 20mm lug width. Quality bespoke makers manufacture straps with precise tolerances that guarantee compatibility without play. Avoid generic or approximate items. A quality strap has perforated holes or slots precisely aligned to specification.

With proper care (air drying after moisture exposure, avoiding persistent rainfall), a taurine leather strap lasts 18–36 months. An alligator in vegetable tanning can reach 4–5 years. Longevity depends on wear frequency and environmental conditions. Vulcanised rubber has indefinite durability if protected from sustained direct UV exposure.