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