Strap for Master Collection Worldtime Black Bracelet

The lug width (ansa measure) of the Longines Master Collection L2.631.4.51.6 is exactly 20 millimetres. To verify strap compatibility, measure the internal distance between the two spring bar pins on the case using a digital calliper: the reading should fall between 19.8 and 20.2 millimetres to ensure proper fit without tension on the case lugs.

For the Master Collection L2.631.4.51.6 in stainless steel with silvered dial, the optimal strap material depends on intended usage: alligator leather with vegetable tanning develops patina organically and maintains classical aesthetics; smooth calf in cognac-brown tonalities offers reduced visual contrast and monochromatic continuity; shell cordovan delivers exceptional durability and natural lustre; NATO fabric in dark grey suits active contexts. We recommend avoiding excessively thick straps (beyond 4mm) as they compromise the proportional balance of a slim case.

Strap removal requires accessing the spring bar pins connecting the lugs to the case. Using a dedicated spring bar tool or soft pry bar, depress the pin pin downward until it disengages from its seat, remove the old strap, align the new strap with the lug holes, and press the pin until you feel the snap back into position. Careful technique is essential to prevent scratching the case finish.

Yes, the Master Collection L2.631.4.51.6 is fully compatible with quality aftermarket straps provided the lug width is precisely 20 millimetres. We recommend artisanal straps in alligator, calf or shell cordovan leather with vegetable tanning, manufactured by specialised ateliers. Mass-produced synthetic leather straps are unsuitable for a timepiece of this calibre.

Leather strap longevity depends on material quality and usage intensity: alligator or vegetable-tanned calf maintain elasticity and structural integrity for 3 to 5 years under daily wear with regular maintenance (dusting, drying after perspiration); shell cordovan, owing to its natural density, often exceeds 7 years of serviceable life. The patina that develops represents aesthetic deepening rather than structural degradation. We recommend rotating between two straps weekly to extend lifespan and avoiding prolonged water immersion.