We use UHMW in all our suspension bushings because it is stiff, has almost zero deflection yet also absorbs some vibration. It will outlast other types of rubber or urethane bushings. When the  E90 is driven hard on the street & on the track, the rear subframe is exposed to extremely large twisting forces. Polyurethane and rubber bushings will deflect and slide, potentially causing your chassis to crack on the subframe mounting points. With our bushings, you won't have to worry about any more flex in your subframe, your rear alignment will stay in check during hard cornering, braking, and acceleration.