Lethal Performance is a direct authorized distributor for Ford Performance who offers two different styles of lowering springs for your S550. A street version and a track version. The street version is designed to lower the car and provide better handling on the street and track while maintaining excellent drivability. The track version uses different spring rates than the street version does which is aimed more for track use. The track springs still lower the car giving it a more aggressive look but are designed mostly to focus on handling and on-track performance.