The Linemount Retro line is designed to be a faithful reproduction for those that have a longing for the guns of the past, without the sticker shock of a collectible original. Whether you have nostalgia for a weapon of your own youthful days, or you were just born too late, these Retro parts will scratch your itch for the "Good Old Days". FeaturesRetro M16A1 Birdcage Flash HiderStandard AR 1/2 x 28 RH threadsRequires standard AR crush washer for installation (not included)For use only with .223 / 5.56mm - DO NOT USE WITH 9MM