The ez aim gong hanger with recoil spring is designed to be mounted on the top of a 2 x 4.It fits most steel targets.The targets are best mounted with a center bolt hole.The recoil spring reduces the impact of the projectiles on the ar500 steel target by absorbing some of the energy.Attaches to the 2 x 4 lumber with a steel wedge that creates tension on the wood.Bolts and hardware are supplied to permanently mount it to the wood.Material: SteelIncludes: Hardware/Recoil SpringWeight: 4.40 lbs