Why would you need these? Well, if your Super Duty is exhibiting the characteristics of worn suspension bushings these poly bushings can make that problem go away. The kit includes front and rear leaf spring bushings, front sway bar bushings and front track bar bushings. Energy Suspension says that their Hyper Flex bushings will provide precise handling and cornering stability while reducing body roll, and the stability offered by the firmer polyurethane bushings also contributes to a great improvement in control under braking and towing. Better performance and longevity are also on tap. Also worth noting is that the bushings are resistant to under-vehicle fluids and contaminants.