These high-performance spring sets are specifically designed to work with the factory struts. These springs lower the vehicle approximately 20mm and increase the spring rate by 25%. This complete kit features Eibach springs manufactured to Prodrive's specifications. This spring kit is available for 2004+ WRX and Impreza. Slalom test with Prodrive's WRX spring kit: Stock WRX: 61.4 mph Prodrive WRX: 67.3 mph