China Rotary Digging Rock Bit 8 1/2" IADC Code 637 with Straight Shank Single Roller Bit Cone 1/2/3 Replaceable Drill Bit, Find details about China Single Roller Bit, Roller Bit from Rotary Digging Rock Bit 8 1/2" IADC Code 637 with Straight Shank Single Roller Bit Cone 1/2/3 Replaceable Drill Bit