Watches need to have glass facings on them so that you can read the time right? But no matter how careful you are about them, the glass does get dinged and prompted with frequent daily use. It's just a normal part of wearing a watch. But the larger the scratch, the worse the glass facing looks and eventually deeper scratches weakens the glass face causing cracks and breaking. The cracks may also allow dirt and water to see into the watch dial, damaging it beyond repair. If you are worried about finding the exact replacement for your glass facing, I think this article can help you out tremendously.
Wrist watches-Most crystals for wrist watches are specially designed for them. The most common shape is round but you do get square, rectangular, and oval shapes which are cut to fit the watch face. The watch glass facings can also be made of several different materials like plastic for acrylic watches, glass for designer gold and dual-toned watches and of course the high-strength synthetic sapphire.
The acrylic crystals are the easiest to source and replace as they can be easily manufactured out of plastics and ground to fit any shape. If the acrylic facing gets cracked or scratched, special pastes can be used to remove the scratches and repair the cracks without removing the acrylic from fused cases. Most acrylic glass facings are fused in to the casings and can not be removed. They also do not have the gasket to prevent water seepage and very water permeable.
Glass on the other hand is mostly available in the form of round facings which are used on round watch faces. But designer watches may need replacement elliptical, square, or even oval glass faces that are not easy to make or find. Watch makers then have to file each round glass piece to fit individual watch faces. If the work is not done carefully, there are chances that there will be a leakage so watchmakers use an adhesive to seal the reworked glass face in to the casing. But almost all mineral glass facings have a gasket next to them to allow for sealing and moisture control.
Sapphire crystals are the best in the market at present but they are expensive. These crystals are commonly used in high-precision time pieces like dive watches or high-quality time pieces like Patek Philippe. The sapphire crystals are difficult to manufacture but are really resistant to pressure scratches and water leakage. This makes them well worth the money and effort to fit them into place. Sapphire crystals have to be locked in place to take in a lot of pressure. Most of them have tension rings to lock them in place and prevent seepage.
Do check with the company to find exactly what you need to replace the glass facings on individual models.