While driving on the bumpy road, the spring seats reduce the vibrations and noise. Every vehicle built today has been provided with spring seats. When driving on rough roads, strong bumps and vibrations are absorbed by the coil spring, and what’s left is taken care of by the coil spring isolators to give a smooth ride. It also keeps the control arms from affecting the coil spring. OE isolators are typically made of rubber, which absorbs vibrations. Because of the constantly shifting weight and pressure, the rubber doesn't last long. Moog's coil spring isolators are made of high-quality rubber and can return the coil spring operation just like new as the OE. If the coil spring is not properly fitted, it can damage the OE isolator. Always trust Moog when replacing the coil spring setup.