Further More proving its mastery of chronographs and exclusively high-frequency precision, ZENITH unveils the DEFY El Primero 21 with a new El Primero calibre beating at a phenomenal price of 50Hz for an correct one/one centesimal of the next chronograph function. Chronographs — with their bezels, scales and sub-dials — https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/