SilencerCo's pistons were designed to be easily changed for different host firearms or calibers. Pistons are built with 17-4 stainless steel then heat-treated for maximum durability. The piston is part of the Nielson device that moves and allows semi-automatic cycling for unlocking pistol barrels. Throw a Fixed Barrel Spacer on for fixed barrel applications. SilencerCo pistons have female threading that attaches to their SilencerCo threaded barrels.Compatible with Omega K Series Hybrid 46 Hybrid 46M with Charlie Piston Mount Osprey Series Octane Series Omega 36M with Charlie Piston Mount