Mining Machinery PartsChina Single Roller Bit with Full Insert 8 1/2" IADC Code 637 Single Roller Cutter Rotary Digging Rock Bit Replaceable, Find details about China Single Roller Bit, Roller Bit from Single Roller Bit with Full Insert 8 1/2" IADC Code 637 Single Roller Cutter Rotary Digging Rock Bit Replaceable