Calibre 2236 Is equipped which has a Syloxi hairspring that is made by Rolex and patented. This silicon hairspring features a patented geometry that ensures the calibre’s regularity in any situation. 6 miles, or 55.7 km) at the end of a 6 weeks’ voyage. (The geographical mile is defined as https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/