On the one hand the Tank, with its essential, dandy aesthetic, on the other the Must concept that made Cartier's luxury codes accessible in the 1980s. In a modern key, they give life to an eco-sustainable watch, powered in some variants by a photovoltaic movement, the SolarBeat, with a 16-year battery life. A technical feat based on the invisible perforation of the Roman numeral hour markers, allowing solar energy to reach the tiny photovoltaic cells hidden beneath the dial. "Today, the Must watches are part of the heritage and legend of the Maison; (...) they owe their timeless character to a style that is recognisable at first glance, as well as to the excellence of their manufacture, which, moreover, characterises all Cartier creations in its attention to the smallest detail," said Pierre Rainero, Cartier's Director of Image, Style and Heritage. Also new is the Altstrap strap combined with the SolarBeat, composed for the 40% of material produced from apple waste grown for the agri-food industry in Switzerland, Germany and Italy. The Maison also offers versions of the new Tank Must that are animated by automatic mechanical movements, with steel bracelets or set with diamonds. Lastly, the coloured versions are worth mentioning. In fact, remaining true to the spirit of the 1980s, the new Tank Must in certain versions is dressed in the three colours that are part of Cartier's DNA according to a monochrome approach, namely red, green and blue. The "coloured" versions with steel cases are characterised by the minimalism of the dial, devoid of both Roman numerals and the "chemin de fer" minute track: a total chromatic look in harmony with the matching straps.