Strap for Master Collection 40 Date Stainless Steel / Silver-Arabic / Alligator XL

The lug width of the Longines Master Collection L2.793.4.78.5 is precisely 21 millimetres. This measurement is exact and non-interchangeable: it represents the spacing between the two soldered lugs on the case. A strap with a lug width below 21mm will leave visible lateral gaps; one above will exert pressure on the case. Correct measurement is performed using a digital calliper positioned perpendicularly across the inner edges of the lugs, from wall to wall.

Nile alligator is the most naturally harmonious choice: its geometrically regular grain aligns with the pure lines of the steel case, and the patina it develops over time adds aesthetic depth. Vegetable-tanned calf leather offers a contemporary alternative with warm, organic patina development. For formal-sporty versatility, a linen NATO maintains coherence with the watch's character. FKM rubber is appropriate for high-humidity environments or dynamic activities.

Strap replacement requires two specialised tools: a spring bar tool and a non-reflective work surface. Position the watch with the lug facing upwards. Insert the flat end of the spring bar tool into the thin aperture between the lug and the passant (leather keeper), applying gentle pressure until the spring bar retracts. The passant will disengage from the case. Repeat for the second lug. Insertion is the reverse process: align the strap end holes over the retracted spring bars, then allow them to snap into position. A specialist atelier such as Casati Milano can execute this operation with professional precision.

An aftermarket strap is compatible only if its lug width is precisely 21mm. Many generic straps are manufactured to standardised dimensions (20mm or 22mm), which are mechanically incompatible with this model. Mechanical compatibility does not guarantee aesthetic coherence: the lug width must proportion visually with the case and original lugs. Bespoke artisanal straps, constructed to custom specifications, ensure both mechanical compatibility and proportional design coherence with the case architecture.

A high-quality alligator or vegetable-tanned calf strap, constructed with hand-stitching, typically lasts 3–5 years under moderate daily wear conditions. Longevity depends on exposure to moisture sources (perspiration, rain, bathing), frequency of wear, and preventive maintenance practices. Vegetable-tanned materials develop pleasant patina through natural ageing, enriching the overall aesthetic. Casati Milano provides an 18-month warranty on all bespoke straps, including complimentary repair and deployant clasp replacement services.