BBK Polyurethane Rear Coil Spring Isolator for Ford Mustang is required when lowering 1979-2004 Ford Mustang models. It is important to also install a set of BBK offset steering rack bushings to eliminate bump-steer. A low profile pinion snubber bushing is also needed to ensure proper axle travel with lowering. BBK's Gripp series polyurethane also ensures that they will greatly outlast the facility rubber pieces. As many enthusiasts will also find worn out spring isolators, sway bar and strut mounts when installing the new lowering springs BBK also offers high quality polyurethane versions, as well as new heavy duty end link kits.