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