A sapphire crystal gives a watch the following properties: extremely high resistance to impact and superior screen and hand readability thanks to?ÿits transparency. Because it is the strongest material after diamonds, it is used in fine timepieces for its anti-scratch prowess. Sapphire crystals can take many forms and give the watch a variety of looks: flat, domed, concave or ground. All Tissot watch cases undergo several tests, including a water resistance check.