This pair of allow steel upper Rear Shock Mount (RSM) reinforcement plates is zin chromate plated for corrosion prevention and is made of a thicket material than the OE (Z3) reinforcement plates.
Many BMWs are prone to sheet metal cracking near the rear, upper shock mount bolt holes. This problem becomes even more likely with track or race use, especially with race grade shocks.
These reinforcements can be used with OEM style rubber RSMs or aftermarket spherical style mounts.