ZRC Grands Fonds MN64 Heterium Rubber: what does its owner think?

The ZRC Grands Fonds MN64 Heterium Rubber embodies a particularly assertive vision of the utilitarian dive watch. A contemporary heir to the original Grands Fonds 300®, this rubber-strap version retains all the technical radicality that defines ZRC while offering a more modern and immediate interpretation of the professional dive watch. With its navy-to-black gradient dial, satin-finished case and FKM rubber strap, this version fully embraces its place in the world of uncompromising tool watches.

The model is listed at 3,390 €.

What makes this reference especially interesting is its ability to combine the aesthetics of a traditional dive watch with deeply distinctive technical solutions. ZRC is not simply offering a robust dive watch: the brand builds an object in which every element responds to a functional logic, whether it is the crown at 6 o’clock, the Crown Protection System™, the ECS® bezel system or the programmed-deformation caseback. The MN64 Heterium Rubber therefore belongs to an approach where technical coherence matters just as much as style.

What are the characteristics of the ZRC Grands Fonds MN64 Heterium Rubber?

Case of the ZRC Grands Fonds MN64 Heterium Rubber

The case of the ZRC Grands Fonds MN64 Heterium Rubber is made of amagnetic 316L stainless steel and uses a monobloc construction with screw-down caseback and crown. Its 41.5 mm diameter gives it strong wrist presence, in keeping with its purpose as a professional dive watch. ZRC also specifies compliance with ISO764: 4800 A/m, which further reinforces its technical profile. The programmed-deformation caseback, exclusive to the brand, is part of the same functional logic. The case is topped by a 3 mm domed sapphire crystal with anti-reflective treatment. 

Dial and readability

The dial of the MN64 Heterium Rubber stands out through its navy-to-black gradient, a combination that gives it visual depth and real personality. This chromatic transition reinforces the model’s contemporary dimension without taking it away from its purely utilitarian register. Readability remains central to the project, in a watch designed first and foremost for diving and professional use. The whole therefore retains a very coherent face, where colour and function are intelligently balanced. 

Bezel, crown and functional architecture

One of the most distinctive elements of this ZRC lies in its diving-oriented architecture. The unidirectional rotating bezel with 60 divisions receives a ceramic insert and relies on the brand’s patented ECS® system, designed to ensure optimal rinsing after a dive and to prevent impurities or salt crystals from accumulating between bezel and case. The screw-down crown at 6 o’clock, with reverse thread, is another strong signature. It forms part of the Crown Protection System™, and the strap cannot even be closed unless the crown is fully screwed down. This unusual solution perfectly expresses the ZRC philosophy: every design detail must also reinforce safety and functionality. 

Movement and performance

The ZRC Grands Fonds MN64 Heterium Rubber is powered by the Sellita SW300-1 “Elaboré” calibre. This Swiss automatic movement beats at 28,800 vibrations per hour (4 Hz) and offers a 56-hour power reserve. The watch displays hours, minutes and seconds in a logic of readability and reliability. ZRC clearly emphasises the seriousness of the movement, chosen to support the robust and professional spirit of the piece. 

Strap and comfort

In this configuration, the MN64 Heterium is fitted with an FKM rubber strap. ZRC describes it as a strap inspired by the design of the metal bracelet, compatible with a steel pin buckle, highly comfortable and available in several colours. This use of FKM is coherent with the diving vocation of the watch: it brings flexibility, resistance and comfort in sporty or aquatic use while also reinforcing the more contemporary character of this Rubber version.

Water resistance and everyday use

The ZRC Grands Fonds MN64 Heterium Rubber stands out through a particularly impressive level of water resistance. The brand states water resistance guaranteed to 1000 metres and tested to 1500 metres, clearly placing it in the category of serious dive watches. This technical capability, combined with the monobloc construction, secured crown and ECS® bezel, gives the model strong credibility within the world of tool watches. Yet despite this radical nature, its gradient dial and FKM strap also allow it to remain wearable in broader everyday use.

ZRC Grands Fonds MN64 Heterium Rubber: a dive watch French in spirit, robust and uncompromising

With the MN64 Heterium Rubber, ZRC offers a dive watch that fully embraces its functional logic. The monobloc case, the crown at 6 o’clock, the ECS® system, the extreme water resistance, the Sellita SW300-1 Elaboré and the FKM strap all come together in a highly coherent whole. This watch will appeal to enthusiasts looking for a true characterful diver that is technically credible, visually strong and faithful to a tradition of engineering-led watchmaking built around real use.

Conclusion

The ZRC Grands Fonds MN64 Heterium Rubber is aimed at enthusiasts looking for a dive watch that is robust, original and technically very complete. Thanks to its unique functional architecture, its impressive water resistance, its proven Swiss movement and its FKM strap, it offers a particularly coherent reading of the contemporary professional diver.

Dialicious owner reviews are a relevant way to choose the watch that truly suits you.

(Updated May 2026)