The only file guaranteed to never wear down, these genuine Czech crystal files are tempered and hardened for durability and safety. When you use a crystal nail file you can feel the difference immediately. It's a very fine filing surface. The grit is permanently etched into the surface of the glass file. Easily washable. 3.5"l x .4"w. Styles and colors are assorted and chosen at random for online orders. If you have a specific style/color you'd prefer please mention that in the comments and we'll do our best to accomodate your wishes.