Strap for Hydroconquest Quartz 39 Green

The lug width of the Longines HydroConquest L3.640.4.06.6 is 20mm. This width was carefully selected by Longines to maintain harmonious proportions between the case diameter (39mm) and the strap width, ensuring balanced aesthetics across different wrist sizes. The 20mm measurement is a standard in the watch industry and provides access to a wide selection of aftermarket straps specifically engineered for this dimension.

The optimal strap choice depends on intended use and aesthetic preference. For luxury pairing, we recommend an alligator strap in cognac-brown or polished black, which creates elegant contrast with the steel case. For those appreciating natural patina development, vegetable-tanned calf leather with fine grain is ideal. If underwater functionality is paramount, an FKM rubber strap in dark grey or black remains the most authentic sports-heritage choice. Shell Cordovan creates a rare and sophisticated aesthetic with patina evolving toward burgundy tones over time.

Strap replacement requires a spring bar tool (a small, inexpensive lever). Position the flat end of the tool beneath one of the metal pins retaining the old strap, apply gentle pressure to release the internal spring mechanism of the pin, then extract the pin from its seat on the case. Repeat for the opposite side. Insert the new strap's pins (confirming 20mm width) into the corresponding seats and verify both pins are firmly seated. The operation takes under one minute with practice.

Yes, provided they feature a 20mm lug width. Quality aftermarket straps offer complete compatibility with the original Longines pins and case seats without requiring modification. Always verify the strap is specifically engineered for 20mm, not adjacent sizes (18mm or 22mm). Reputable manufacturers such as Casati Milano produce bespoke aftermarket straps with double stitching, artisanal finishing, and extended warranties, often surpassing OEM strap quality.

Leather strap longevity depends on material, usage patterns, and maintenance discipline. Standard calf leather typically lasts 2–4 years with daily wear and protection from excessive moisture. Alligator or Shell Cordovan, owing to denser fibre structure, may endure 5–8 years or longer with proper care. FKM rubber straps offer comparable durability (4–6 years) but require regular cleaning to prevent degradation. Casati Milano provides 18-month warranty on all straps and furnishes guidance on maintenance (cleaning, drying, conditioning with specialist creams) to extend strap longevity.