The Geissele AR15 Super 42 Wire Buffer/Spring Combo is a concept that is similar to a spring that was used in the German MG4 machine gun. The unique spring design utilizes three independent strands of wire which helps to act as a harmonic damper and energy absorber. The springs can flex separately from each other which allows you to displace excess energy which decreases the overall chance of having a spring failure. The result of installing this kit will be improved function along with enhanced reliability with your AR-15 platform rifle. Additionally the Super 42 features a 15% stronger average return force than the standard buffer spring and as such the use of .300 AAC Blackout Subsonic loads is not recommended.