Angstadt Arms Hydraulic Buffer Kit, Standard Damping Profile, 6 oz, Stainless Steel, For 9MM/.40 S&W/45 ACP AR Rifles, Includes Buffer with Spring AA09HBKSDP Hydraulic buffer kit smooths out the recoil impulse of a straight blowback PCC. The standard damping profile is best for primarily unsuppressed applications in barrels of all sizes.