Vaper 19747 1/4-Inch NPT Straight Air Die Grinder features a free running speed of 22,000 rpm and air inlet size of 1/4-Inch NPT. Grinder cap is 1/4-Inch and air consumption is 4.5 cfm. Suggested air compressor is 1.5 HP, suggested air hose size is 3/8-Inch, and suggested air pressure is 90 psi.