China 8 1/2" IADC Code 637 Single Roller Bit with Full Insert Roller Bit with Straight Shank Rock Drilling Tools Replaceable Bit TCI, Find details about China Single Roller Bit, Roller Bit from 8 1/2" IADC Code 637 Single Roller Bit with Full Insert Roller Bit with Straight Shank Rock Drilling Tools Replaceable Bit TCI