Gemtech SFN-57 5.7 X 28 suppressor. Built to handle the back pressure of 5.7 X 28 with supersonic FN ammo or subsonic. Great silencer for PDWs, FN Five-Seven pistols or AR Five-Seven carbines. Can also be used for .17HMR, .22LR, .22WMR and lesser caliber. M 10 X 1 MM. Class III item. NFA rules do apply. New.