The Powerflex USA Rear Subframe Rear Mount Inserts - PFR51921 are a set of polyurethane bushings designed to replace the factory rubber bushings in the rear subframe of a vehicle. These inserts provide increased stiffness and improved handling by reducing subframe movement and flex. They also help to eliminate any unwanted play or movement in the rear suspension, resulting in a more precise and responsive driving experience. The inserts are made from high-quality materials and are designed to be a direct replacement for the OEM bushings, making installation quick and easy. These inserts are compatible with a variety of vehicle makes and models and are a popular choice among performance enthusiasts looking to improve the overall handling of their vehicle.