Strap for Horological Machine N°4 HM4 Final Edition

The lug width of the MB&F Horological Machines 42.BTSL.B is 20mm. This dimension is specific to the asymmetrical case architecture and permits the use of straps calibrated exclusively to this measurement. The lug width is measured by positioning a ruler between the internal attachment points, excluding the case shoulders.

For the 42.BTSL.B, straps in alligator leather with vegetable tanning are ideal, as they harmonise exceptionally with the titanium case. Valid alternatives include aged vegetable-tanned calf leather in matte finish, cotton NATO straps for an informal approach, and FKM rubber for sporting use. The choice depends on context and personal aesthetic preference.

Strap changing requires a quality spring bar tool to avoid damaging the lugs. The procedure involves carefully removing the elastic pins from the lugs using the tool, extracting the worn strap, and inserting the new strap by pushing the pins to their housing. If uncertain, it is advisable to consult a specialist atelier such as Casati Milano to ensure risk-free service.

Yes, it is possible to use quality aftermarket straps provided they are certified for the 20mm lug width. Milano Straps offers a specialised selection of 20mm straps tested and verified for compatibility, manufactured in noble materials such as alligator, calf leather, and technical rubber. Compatibility is guaranteed by conformity to lug width specification and construction robustness.

A superior quality leather strap (vegetable-tanned alligator or calf leather) worn daily on a timepiece of this significance has an average lifespan of 3 to 5 years, depending on usage intensity and climatic conditions. Leather ages naturally, developing a patina that enriches its aesthetics. Factors such as perspiration, humidity, and solar exposure accelerate wear. Periodic maintenance (cleaning and conditioning) significantly extends longevity.