China 8 1/2" IADC Code 637 Single Roller Cutter with Straight Shank Roller Cones Bit with Cones 1/2/3 Replaceable, Find details about China Single Roller Bit, Roller Bit from 8 1/2" IADC Code 637 Single Roller Cutter with Straight Shank Roller Cones Bit with Cones 1/2/3 Replaceable