Jewelry Twofers Grinder BitsAanraku TWOFERS 3 4 inch 600 grit ultra fine glass grinding bits (2 bits per package) Two Bits for the Price of One! Aanraku brings you Twofers superior quality, low cost grinding bits. Use jewelry bits to grind a groove into the edges of jewelry for finishing and wire wrapping. The groove created in the edge of the cabochon fits 20 gauge wire for a secure wire wrapped finish. A huge time saver! Best of all, your jewelry pieces will be more durable.