This is for a pair of adjustable height rear spring platforms, designed to work with 60mm inner diameter coilover rear springs mounted in the stock spring location at the rear of a BMW E8x (1 and Mseries) or E9x (3 and M series). These are high quality products made by HPA right here in the USA, with easy adjustments. The thread used is self locking once any load is applied.
The material for the rest of the assembly is made up of black and HPA blue anodized aircraft grade aluminum alloy. These can be adjusted from a minimum of 0.5" thick to a maximum of 2.75" thick. These can be adjusted independently of each other and is great for corner balancing of your BMW.
This particular model has been optimized to run at the top of the spring on the back of a BMW E8x/E9x. The locating stub fits in the factory location and replaces the bulky factory locating stub/hat, which inhibits ride height adjustment with other similar rear ride height adjusters.