Overview

Carbon TPT® case with the RMUL4 calibre

The RM 55-01 Manual Winding was introduced in April 2026 in three case executions — Carbon TPT®, White Quartz TPT® and Grey Quartz TPT® — built around a new calibre, the RMUL4. The movement is a manual winding skeletonised construction indicating hours, minutes and seconds, and weighs under five grams. The absence of an automatic rotor leaves it open to view from both sides.

The three-part tonneau case is smaller than the RM 055 that precedes it in the family. The bezel and caseback are the composite and the case middle is titanium. The calibre is anchored by four microblasted titanium spline screws, framed by satin-finished pillars and polished bezels, and the microblasted rhodium-plated hands run above a four-part flange combining titanium, carbon fibre and steel.

Key details

Design and engineering

• Calibre RMUL4Manual winding skeletonised movement with hours, minutes and seconds. Movement dimensions are 31.25 × 29.45 mm with a thickness of 3.46 mm, running on 26 jewels at 28,800 vph (4 Hz), and the whole weighs under five grams.
• Baseplate and bridges in grade 5 titaniumThe baseplate is grade 5 titanium, microblasted and sanded; the going train is held by three bridges, also grade 5 titanium, sanded and treated with Titalyt®. The thicker satin-brushed structural parts are worked to the same tolerances.
• Free-sprung balance with variable inertiaThe regulator index is eliminated and calibration is made by four small adjustable weights fitted directly to the balance. The balance is Glucydur®, four arms, moment of inertia 4.8 mg·cm², angle of lift 53°, with an elinvar balance spring by Nivarox® and a Triovis No. 2 index assembly.
• Double-barrel systemStored energy is distributed across two barrels rather than one, increasing the number of rotations and reducing pressure on the teeth, bearings and pivots.
• Carbon TPT® caseCarbon fibre threads are divided into layers no thicker than 30 microns, saturated in resins developed for Richard Mille, and stacked by an automatic positioning system that rotates the fibre orientation by 45° between layers. The stack is heated to 120°C under 6 bar of pressure and then CNC-machined at the brand’s own facilities. The resulting damascene striation is unique to each case.
• Flanges and crystalsThe upper flange is grade 5 titanium with index points filled with approved luminous material; the lower flanges are polyamide and 316L stainless steel. Both crystals are sapphire at 1,800 Vickers with anti-glare treatment on both faces. The bezel-side crystal is 1.00 mm at its thinnest; the caseback is 1.55 mm at the centre rising to 2.29 mm at the outer edges.

Specifications

Technical specifications

Buying with HYPA

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• Manufacturer warranty confirmed from the warranty card
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• Registered Australian dealerHYPA International Pty Ltd · Victorian Second-Hand Dealer Licence SHD-0018017.
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Related references

RM 055

Richard Mille · RM 055 Yas Marina Circuit Edition

RM 55-01

Richard Mille · RM 55-01 White Quartz TPT

RM 056

Richard Mille · RM 056