Calibre 2236 Is fitted with a Syloxi hairspring that is made by Rolex and patented. This silicon hairspring incorporates a patented geometry that assures the calibre’s regularity in any posture. 6 miles, or 55.7 km) at the end of a 6 weeks’ voyage. (The geographical mile is outlined as 1 https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/