Progress Tech Sport - lowering springs will significantly improve vehicle appearance and handling capability. The lowering will improve appearance and lower the center of gravity. Sport - tuned spring rates will enhance vehicle handling capability and reduce the body roll while offering a fun and sporty ride quality. These spring kits are designed to work with OEM shocks, and will benefit from using high performance dampers such as Bilstein, Koni or Tokico. Our engineering staff has decades of experience in the design and tuning of performance suspension systems, including CARTIndy Cars, IMSA, SCCA, NASA, and SCORE competitors. Progress specifies only certified high - tensile SAE spring wire materials. Our coil springs are cold - wound on modern CNC coiling machines, then stress - relieved, pre - set and shot - peened for maximum durability. The springs are then powder - coated for an attractive and durable finish.