Diamond Drilling ToolsChina 8.5 Inch IADC 637 Core Barrel Single Roller Cone TCI Drill Bit 617 Cutter Bit, Find details about China Core Barrel Roller Cone Drill Bits, Single Roller Cone Bit 617 from 8.5 Inch IADC 637 Core Barrel Single Roller Cone TCI Drill Bit 617 Cutter Bit