Kynshot hydraulic buffer ar-9 carbine w/coll stock 9mm FEATURES:-Made from 17-4 stainless steel & uses hydraulic shock absorption to dampen the impact of the boltat the rear of its travel-It's weight & length have been optimized so that it runs reliably, softens recoil, smooths out the action, &stops just behind the bolt catch using any 9mm ammo type-Smoothest running, softest recoiling 9mm buffer on the market