Further Proving its mastery of chronographs and especially high-frequency precision, ZENITH unveils the DEFY El Primero 21 that has a new El Primero calibre beating in a phenomenal amount of 50Hz for an precise one/a hundredth of the 2nd chronograph function. Be event ideal: Don't forget the basic principles: black https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/