Why it's a big deal?? Sapphire crystal is harder than almost everything else on earth, with the exception of materials such as diamonds or tungsten carbide. Double domed indicates it's round on the outside and inside which means it doesn't distort when you look at your watch from an angle. Many domed crystals are only round from the outside creating a lens which distorts the watch face. Our double domed sapphire crystal is produced in Switzerland by Stettler Sapphire.