The 1" medium grit bit from Aanraku fits most glass grinders and provides a cleaner edge than rougher bits. This work well for copper foil work and have less chipping than more coarse bits.Twofers Grinder Bits offer superior quality at a low-cost. The diamond abrasive grinding surface is double plated for strength, durability and long life. It's large 18mm bit height gives you a larger grinding surface, designed to maximize bite and allows for the uniform grinding.