Two Superior Quality Bits at One Value Price Aanraku's 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. Diamond coating guaranteed not to peel! 60 diamond mesh grit and 1" diameter. Use it to quickly and aggressively grind away at the glass. Bits fit most glass grinders.