Strap for Master Collection 40 Moonphase Stainless Steel / Black-Roman / Alligator

The lug width of the Longines Master Collection L2.909.4.51.7 is 21mm. This measurement refers to the internal distance between the lugs (the attachments that connect the case to the strap). You can verify this by measuring with a digital calliper or checking the marking stamped on the original Longines strap.

For the Master Collection L2.909.4.51.7, we recommend a high-quality alligator or calf leather strap. Natural alligator, with its regular scale texture, pairs perfectly with the ordered geometry of the 40mm case, whilst calf leather offers a more contemporary and urbane appearance. Both materials preserve the aesthetic dignity of the watch and ensure longevity.

To change the strap, obtain a spring bar tool or contact a trusted watchmaker. Gently remove the spring bars from the lugs, extract the old strap and insert the new one, ensuring the bars return firmly into position. Avoid forcing to prevent damage to the lugs. By appointment, the Casati Milano atelier performs this operation with precision.

Yes, any strap with a 21mm lug width is compatible with the Longines Master Collection L2.909.4.51.7. It is essential that the lugs (the lateral parts of the strap) are slightly wider than the lug width to slide smoothly around the case. Online you will find a selection of compatible 21mm straps, customisable in material, colour and size.

A high-quality leather strap (alligator, calf, shell cordovan) typically lasts 5-10 years with daily wear, developing a natural patina over time that increases its character. Durability depends on humidity exposure, perspiration and maintenance frequency. Casati Milano guarantees 18 months on its handmade straps and can provide assistance for reconditioning aged leathers.