MB&F · Horological Machines

Strap for Horological Machine N°4 HM4 Only Watch

Integrated bracelet: measurements, the most common questions, and the way to a made-to-measure strap.

Integrated bracelet

The MB&F Horological Machines 41.TSL.OW is designed with a bracelet integrated into the case. For a compatible made-to-measure strap, the Casati Milano atelier builds it on your watch.

Case diameter54 mm
Reference41.TSL.OW
FamilyHorological Machines
MovementMB&F caliber HM4 Hours, Minutes | Power reserve indicator
Year2011 - 2011
CaseTitanium, Sapphire

Spring bar

Swiss Standard universal spring bars

The right category for this model · 316L steel, all lug widths 13–26 mm

The Horological Machines 41.TSL.OW, seen from the bench

The HM4 represents MB&F's interpretation of the aeronautical watch concept, with a design that evokes aircraft turbines. The timepiece is equipped with the MB&F HM4 caliber that indicates hours, minutes and power reserve through laterally positioned displays. The case features a distinctive three-dimensional shape that houses the unconventional movement configuration.

Frequently asked questions

Can you fit a standard strap to the MB&F Horological Machines 41.TSL.OW?

No. The lug attachment is an integral part of the case architecture and does not accommodate standard straight bar lugs. A bespoke strap exists, however, and must be built to measure directly onto the watch: this is the exclusive project of the <a href="/pages/casati-booking">Casati Milano</a> atelier, which measures the specifications during consultation and crafts the piece in complete harmony with the MB&F design.

How is a bespoke strap constructed for this model?

The Casati Milano atelier examines the proprietary attachment during an in-house appointment. Precise geometry, internal diameter, depth, and all constructive specifications are documented. The strap is then hand-crafted, tested, and adjusted on the watch itself until personal fit and comfort are achieved. No off-the-rack production: pure tailoring.

Which leather suits the character of the MB&F Horological Machines 41.TSL.OW?

The satin-finished titanium case and minimalist design naturally dialogue with textured leathers: alligator, crocodile, or lined canguro speak the same language as the aesthetic. The Orange Wave benefits from deep brown with natural patina or vegetable-tanned black aged in time. Every choice is discussed in the atelier to ensure chromatic and visual coherence.

How long does a well-crafted strap last?

An artisanal strap made from quality leather and tailored stitching resists 8–12 years of daily wear, often considerably longer with occasional maintenance. The leather ages naturally, developing patina and character that increase aesthetic value over time. It is not consumable; it is an investment.

Why does the MB&F 41.TSL.OW require a bespoke approach to the strap?

Because Maximilian Büsser conceived the lug attachment as part of the case's architectural language, not as a standardised slot. A custom-made strap honours this visionary approach, transforming the piece from an interesting timepiece into a coherent wearable sculpture. This is the difference between owning a watch and understanding a masterpiece.

The next step

The right strap isn't chosen. It is built, together.

From the atelier appointment to delivery, every step is made for those who know that things done well take time. Rare leathers, one piece at a time, eighteen months of warranty.

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Casati Milano · Via XX Settembre 15, Milan · by appointment only