This AAC Piston enhances the versatility of an AAC Silencer by allowing the suppressor to be swapped between various host firearms with different barrel threads. All that is necessary to convert the silencer to be compatible with a different barrel thread pitch is to select the proper piston and replace the existing one residing in the rear of the sound suppressor. All AAC pistons are constructed of heat-treated stainless steel with a bead blasted matte finish, and each is engraved to indicate the thread diameter, thread pitch and direction of rotation for installation. WILL NOT WORK WITH TI-RANT 9M-HD SILENCERS.