The Koni Special Active Shock FSD 06-11 BMW 3 Series AWD (E90) Rear is a suspension system designed to improve the driving dynamics of the BMW 3 Series AWD (E90). It features a patented Frequency Selective Damping (FSD) technology that allows the shock absorber to automatically adjust to road conditions in real time. The shock absorber is designed to provide a comfortable ride while still providing excellent handling and control. It is also designed to reduce body roll and improve cornering performance. The shock absorber is constructed from high-quality materials and is designed to last for many years.