Calibre 2236 Is equipped that has a Syloxi hairspring that is made by Rolex and patented. This silicon hairspring features a patented geometry that guarantees the calibre’s regularity in almost any situation. There you have it, 5 brands that have played a big function in the event of the chronograph. https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/