Its unique Short Energy Pulse system reduces length of recoil so that repeating shot energy cannot overlap and knock the shooter off target.Full auto fire is possible with massively reduced recoil and muzzle climb, meaning that all shots fall on target. SPECIFICATION:Caliber: 5.56X45mm / .223Material: Hardened Milspec Steel Finish: Black Nitride QPQDimensions: L: 2.570”, DIA Body: 0.866”Weight: 3.2ozThread: 1/2-28 UNEF R/HSerial Numbered for Quality Control Comes with appropriate crush washer. NOT considered a flash hider – California legal. Made in the USA.