Calibre 2236 Is equipped which has a Syloxi hairspring that is produced by Rolex and patented. This silicon hairspring features a patented geometry that guarantees the calibre’s regularity in almost any posture. There you've got it, 5 brands that have performed a massive purpose in the event from the chronograph. https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/