Even Further proving its mastery of chronographs and specifically superior-frequency precision, ZENITH unveils the DEFY El Primero 21 using a new El Primero calibre beating at a phenomenal rate of 50Hz for an correct one/a hundredth of the second chronograph perform. I'd happily use Watches World again and would recommend https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/