China 8 1/2" IADC Code 637single Roller Cutter with Basis Rock Drilling Tools Rotary Digging Machine Roller Cones Bit with Full Insert, Find details about China Single Roller Bit, Roller Bit from 8 1/2" IADC Code 637single Roller Cutter with Basis Rock Drilling Tools Rotary Digging Machine Roller Cones Bit with Full Insert