Even Further proving its mastery of chronographs and precisely superior-frequency precision, ZENITH unveils the DEFY El Primero 21 by using a new El Primero calibre beating in a phenomenal level of 50Hz for an accurate 1/one hundredth of the next chronograph function. Suitable for people who value straightforwardness around precision, https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/