The Bilstein PSS9 coil over suspension kit provides the perfect balance for both spirited street use and track racing. The fully-adjustable monotube gas shock absorbers offer a selection of nine precise compression and rebound settings, from comfort to competition. Patented digressive piston head design and deflective valving instantly reacts to changing road conditions. Monotube design dissipates heat more effectively than a twin tube shock for cooler, more efficient operation and longer life. The spring rates are more aggressive than stock, for quicker suspension response and better handling. Ride height is fully and precisely adjustable. This is the approved suspension kit for SPB, BSR and BSX Spec racing.