These are made by a company that sells the new springs that raise the rear of the car. They claim that this will lower the rear 1.25" from a pair of these. Obviously these only work on 1/4 elliptic cars. We have found that the amount of lowering varies by car, but this is pretty close most of the time. We also carry some different styles which are a little easier to install and come in more sizes to fine tune. These are sold individually so if you want to lower both sides, you'll need 2.