These performance polyurethane components help reduce common wheel roll - under. This occurs when stopping abruptly, especially when using performance tires. For both front of rear drive vehicles is so equipped. Replaces that original, short lived and too - soft O.E.M. rubber. On front wheel drive vehicles - diminishes wheel hop and traction loss during standing start accelerations. Better maintains proper alignment under extreme conditions. Made of Energy's Hyper - Flex(TM) performance polyurethane to add both performance and durability.