Gison GPW7 4-Inch Air Wet Stone Polisher 4500 Rpm with Front Exhaust Air Cons: 0.22 m3/min 8 CFM minimum 12 CFM optimal Spindle Size: 5/8-11 one 4" back holder (Semi Rigid) Max Speed: 4,500 rpm Weight: 1.36 kg (3 lbs)