The Armaspec enhanced buffer tube kit contains all the necessary parts required to mount a stock assembly on to a lower receiver. The buffer tube kit contains a mil-spec 7075-T6 6 position buffer tube a steel castle nut and end plate as well as an SRS GEN4 the enhanced multistage recoil buffer system. The Stealth Recoil Spring (SRS) GEN4 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.