Strap for Master Collection 40mm Annual Calendar Stainless Steel / Black-Roman / Alligator

The lug width (also known as strap width) of the Longines Master Collection L2.910.4.51.7 is 21mm. This specific measurement is determined by the internal distance between the watch case lugs. To verify, measure the distance between the two metal pins that attach the case to the strap; the value should be exactly 21mm.

The optimal strap choice depends on intended use and aesthetic preference. Alligator leather with vegetable tanning represents the premium option, as its natural grain pattern harmonises with the dial's rigorous design. Brushed calf offers a more pronounced texture and casual appearance. For versatile daily wear, shell cordovan or robust canvas NATO straps maintain the Master Collection's functional character.

Strap replacement requires a spring bar tool. Position the tool's flat end into the small hole beneath the lug pin, apply gentle pressure to disengage the pin from its seat, then remove the old strap. Align the new strap's holes with the pins and verify that both spring bars are fully secured. If unfamiliar with the process, consult a qualified watchmaker.

Yes, aftermarket options in 21mm lug width are available, although this dimension is less common than 18mm, 20mm, or 22mm sizes. To ensure construction quality and aesthetic compatibility with the Master Collection's understated character, we recommend artisanal straps in alligator, calf, and shell cordovan, custom-made by specialist manufacturers such as Casati Milano.

Leather strap lifespan depends on material quality, construction standards, and usage intensity. An alligator or vegetable-tanned calf strap typically lasts 3-5 years of daily wear. Shell cordovan, owing to its material density, can endure 7-10 years of regular use. Consistent maintenance—gentle cleaning with a damp cloth and protection from excessive moisture—significantly extends strap longevity.