China 8 1/2" IADC Code 637 Single Roller Bit with Cone 1/2/3 Roller Cones Bit Replaceable Bit Rock Drilling Bit, Find details about China Single Roller Bit, Roller Bit from 8 1/2" IADC Code 637 Single Roller Bit with Cone 1/2/3 Roller Cones Bit Replaceable Bit Rock Drilling Bit