UMI Performance 64-72 GM A-Body Rear Lift Bar Set-Up-Weld-InThe UMI rear lift bars replace the factory rear control arms adding traction while not changing vehicle ride height. Lift bars work with axle torque to load the chassis of the car, forcing the rear wheels downward pushing the tires into the ground resulting in harder launches and improved 60 foot times. The UMI lift bars are designed to improve traction and reduce unwanted wheel hop. Lift bars are constructed of boxed mild steel tubing, 1 8" thick