Fits .308 caliber Modern Sporting Rifles, and other .30 caliber and smaller rifles, with thread pitch 5/8-24. Six opposing side ports direct gasses outward, effectively countering muzzle rise and recoil. Easy installation, secured with the supplied lock-nut. Made of 4140 steel with a manganese phosphated finish, measures 15/16" diameter and 2 3/8" length. Weight including locking nut is 3.70 ounces.