These Solid Polyurethane bushings are much harder compared to the soft rubber OEM units. By replacing them with these harder Polyurethane units you are able to get rid of the unwanted slop and flexing of the stock units which allows for the power to go into rotating the tires, instead of flexing the rubber. Giving you better feedback, sharper response, more predictability on throttle input, along with eliminating annoying clunking during hard shifts. These replace Mustache bar inserts only. Side diff inserts sold separately.