The Armaspec Stealth Recoil Spring SRS is a self-contained multi-stage drop-in replacement for your standard buffer and spring. The SRS is designed to keep the buffer spring from rubbing against the inner wall of the buffer tube providing smooth, quiet operation and the second stage helps reduce the felt recoil significantly. FeaturesDrop-in replacement for standard buffer and springReduce felt recoilKeep the buffer spring from rubbing against the inner wall of the buffer tubeBuffer mass is designed to stay under constant tension against the bolt carrier Note: The GEN4 version does not have the O-ring on the weight