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