The Geissele Super 42 Spring was designed to improve the function and reliability of your AR-15 pattern rifle. Its unique spring design uses three independent strands of wire, just like the German MG42 Machine Gun. This concept acts as a harmonic damper and energy absorber by allowing the springs to flex separately from each other. This flex helps displace excess energy which decreases the chance of spring failure and assists with making your AR-15 more reliable. The included buffer is H1 weight. The Super 42 spring and Geissele buffer are designed to work together as a set; the spring will not fit over a standard buffer. If installed with a standard buffer damage to th Mfg: Geissele Automatics