Even Further proving its mastery of chronographs and specially superior-frequency precision, ZENITH unveils the DEFY El Primero 21 that has a new El Primero calibre beating at a phenomenal amount of 50Hz for an exact 1/a centesimal of the second chronograph functionality. My knowledge with the vendor, was truly excellent. https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/