UMI Performance 05-10 Ford Mustang Adjustable Upper Control Arm- Poly Bushingshis upper rear control arm replaces the factory stamped upper control arm reducing wheel hop and increasing traction. The S197 Mustang chassis uses a 3 link rear suspension system with a panhard bar to control the rear end under the vehicle. Under hard loads the factory pieces tend to flex and rubber bushings deflect leading to poor traction and erratic handling. Replacing the factory pieces with stronger well designed items eliminates this flex