On the rear, the closed-cell foam upper shock absorber bushes are a concern area. Used to isolate the damper from the body of the vehicle, age and usage can soften the foam allowing for movement of the damper shaft which inevitably leads to knocking and a loss in damper efficiency. PFR25-930 Rear Upper Shock Mounting Bush is made in our Yellow 70ShA material to replace the OE foam bush, restoring damper location and performance.