3/4" Course Twofers Grinder BitsAanraku TWOFERS 3 4 inch 120 course grit glass grinding bits (2 bits per package) 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 coat guaranteed not to peel!