This is it-the part that everyone wants but can't have. This little rubber bushing is perhaps the most critical component of the kit. Containing a blend of special rubber compounds, Ford spent a fortune on its development, and then once perfected, had Tenneco (Rancho's parent company) supply them along with several other rubber bushings for all '05 Super Duty pickups. The bushing is used in the upper mount of the factory control arms. The patented compound is both strong and soft, which helps isolate road vibrations from the chassis. Thanks to the unique partnership between Ford and Tenneco, those who choose the Rancho 4-inch system will relish in the better-than-stock feel this little bushing contributes.