The Lower Control Arms are boxed and constructed from HSLA steel making them significantly stronger than the stock stamped steel arms. They are equipped with high durometer polyurethane bushings instead of the stock, soft rubber bushings to reduce suspension deflection resulting in improved handling, traction, and performance from the rear suspension system. Adjustability allows the factory eccentric adjuster (which is prone to slipping causing unwanted changes to alignment settings) to be eliminated using the provided eccentric eliminator washers.FE4 = 2012-15 SS V8FE5 = 2012-15 ZL1 V8