Drop-in replacement for standard buffer and spring Reduce felt recoil Keep the buffer spring from rubbing against the inner wall of the buffer tube Buffer mass is designed to stay under constant tension against the bolt carrier Made in the U.S.A. Lifetime Warranty SPECIFICATIONS: Length: 7.18″ Actual Wight (Complete System): Standard: 5.93 oz. Heavy: 6.56 oz. H2: 7.62 oz. 9MM: 8.40 oz. Equivalent Weight: Standard: 3.3 oz. Heavy: 3.8 oz. H2: 4.7 oz. 9MM: 5.4 oz.COMPATIBILITY: AR15 with carbine-length buffer tubeAR10 version is available please find under AR10 parts.The SRS™ can be installed with or without a buffer retainer. The polymer bumper goes towards the rear of the firearm and the metal weight mass goes towards the bolt carrier.