Features:

• Works great on all natural materials
• Ceramics, Tile, Glass, Bone & Wood
• Great for Carving, Grinding, Sanding, Etching and more...
• Long lasting when coolent is used

Rating : - Very good, very cheap, I'm glad!
I tried to make some drawings on a piece of glass and it works fine, the case is very beautiful and the bits seems to have a very good quality. I put one bit into my CNC machine and I was able to drill crystal.