PowRyte 1/4-Inch Mini Straight Air Die Grinder Kit Compact and lightweight design permits easy access to tight areas Paddle throttle lever provides smooth control with less hand fatigue. Built-in silencing reduces noise level; Screened inlet filter ensures no unwanted particles Includes 5 most frequently used grinding stones for grinding, polishing, de-burring and smoothing 25,000 RPM Free Speed @90PSI, 1/4" Collet. Air compressor needed.