Strap for Series 240 C

The Sinn 240.021 features a lug width of 22 millimetres. This measurement is the professional standard for watches of 43mm diameter and is essential to verify before purchasing an aftermarket strap. You can measure it using a calliper, positioning the tool on the inner lug seat of the case, between the inner edges of both lugs. Even minor deviations from this specification result in mounting incompatibility.

There is no universal choice: it depends on intended use. For professional and formal contexts we recommend vegetable-tanned calf or alligator, which develop natural patina and maintain sober elegance. For operational or humid environments, technical rubber is ideal: it resists water, does not oxidise and guarantees grip. A NATO strap in dense cotton is the versatile solution for those alternating contexts. Ideally, an owner should have at least two compatible straps to rotate according to occasion.

Strap replacement requires specific tools: a spring bar remover or a bar with appropriate slots. Position the watch on a stable, soft surface, identify the spring bars securing the strap to the lugs (visible from the case shoulders), and carefully extract with perpendicular motion to the case. Once the lugs are freed, the old strap slides away. Insert the new strap aligning the holes and reinsert the spring bars with uniform pressure. If you lack experience, consulting a professional watchmaker is advised.

Any strap with a certified lug width of 22mm is compatible. Options range from artisanal leather straps (calf, alligator, shell cordovan), to technical NATO straps in ballistic polyamide, to vulcanised rubber straps. Always verify that the supplier clearly specifies lug width: 22mm is the standard for this model. High-quality artisanal Italian-made straps offer customisation in colour, finish and length, adapting to wrists of different circumferences.

Durability depends on usage, material and maintenance. A quality calf or alligator strap typically lasts 18–36 months of daily wear. Constant exposure to sweat, water and UV rays accelerates ageing. A shell cordovan strap, given the dense nature of the leather, may last longer if kept dry. Maintenance includes regular cleaning with a damp cloth, application of protective balm every 2–3 months and periodic rest of the strap to avoid constant stress. If you use the 240.021 in humid environments or high-activity settings, consider rotating between two straps to extend overall durability.