The Geissele Super 42 Braided Wire Buffer Spring and Buffer Combo has a unique spring design made of three independent strands of wire. This acts as a harmonic damper as well as an energy absorber by allowing the springs to flex separately from each other to displace excess energy. The result is a more reliable spring which also removes the annoying spring reverberations (twang) heard by the shooter. The Super 42 Spring has a 15% stronger average return force than the standard carbine buffer spring which helps when operating a dirty weapon or when using steel-case ammo. Not Compatible with Rifle Length or A5 Buffer Tubes/Receiver Extensions.