Ford F-250 Super Duty Skyjacker Leaf Springs Suspension F9320 Softride Add-a-leafs use only American steel and are shot-peened with hard steel pellets at very high velocities. This shot-peening compresses the surface of the steel thereby increasing the tensile strength of the leaf. Without this shot-peening procedure, the maximum wheel travel and ride quality could not be achieved without sacrificing the life of the leaf. The Skyjacker add-a-leafs are pre-drilled for the center pin. Pin location varies with each application. Most have long tapered ends for a progressive affect and ride comfort.