Mineral glass, also known as real glass or tempered glass, has a significant drawback in practice: it breaks and shatters. Even a slight bump can be enough to damage the glass. This disadvantage diminishes the actual benefit that real glass is very scratch-resistant. It's comparable to eyeglasses. The advantages of plastic lenses outweigh the minor drawback that plastic does not have the same scratch resistance as mineral glass, making it a worthwhile trade-off.