Plexiglass and acrylic are one kind of things. Advanced high-quality plexiglass is called acrylic. This material looks as transparent and bright as glass, but some plastics are not fragile and have strong pressure resistance. This is a kind of Polymer materials are industrial products, and crystal is a kind of natural ore, which is formed naturally just like a stone. Better crystals look as transparent and bright as glass, but they have a higher hardness and are as hard as a stone. It does not have the flexibility of acrylic.