Geissele Automatics 04308F: The Super 42 Rifle Length Spring for the M-16/AR-15, brings you the performance and user experience improvement of the Super 42 spring for your rifle length buffer tube. This unique spring design uses three independent strands of wire, that 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 M-16/AR-15 rifle more reliable while diminishing the twang sound from the butt-stock. The Geissele M-16/AR-15 Super 42 Rifle Length Spring works with a standard rifle length buffer and buffer tube.