Rugged Suppressor OEM Piston Copper 1/2"-36 tpi Rugged Suppressors Piston uses a Non-Slotted Design creating a Full Circumference Gas Seal. This Drastically lowers Gas Blowback For a More Enjoyable Shooting Experience. Machined From 17-4 Stainless Steel And Heat Treated This Piston Is Built To Last. *When using a Piston On a Fixed Barrel Platform Such as a Carbine Or subgun The Spring Must Be replaced With a Fixed Barrel Spacer. Model: OEM Material: 17-4 Stainless Steel Thread Pattern: 1/2"-36 tpi Finish: Copper