AIR DIE GRINDER KIT 1/4"(6MM) 10 STONES.DEBURRING, POLISHING, GRINDING.FREE SPEED 22000RPM. AIR USE 4.5 CFM.The Air Die Grinder Kit features a 1/4" (6mm) die grinder with a free speed of 22,000 RPM and includes 10 stones for deburring, polishing, and grinding applications. It requires an air supply of 4.5 CFM to operate.