PST's brand new H.D. POLYGRAPHITE Rear Leaf Spring Bushing Shackle Kit fills the gap in the chain-of-power/torque transfer to the wheels. Our POLYGRAPHITE allows for a smoother uninterrupted transfer of power. You will see a reduction in wheel hop and near zero deflection in PST's bushings. To cap it off, our robust H.D. shackles are zinc-plated to withstand years of road use.