SilencerCo Thread Protector 1/2X28, Barrel Adapter, Black AC6 When transporting your firearm or waiting on ATF approval" you can keep your threads crisp and protected with a thread protector. Careful not to cross-thread" simply twist the thread protector on the end of your barrel to prevent dust and debris from clogging your threads when no silencer is in use. Delta accessories are compatible with Switchback 22" Sparrow 22" Spectre 22" Warlock 22" and Osprey Micro 22.