The Koni Special Active Shock FSD 99-05 BMW 3-Series E46 RWD Rear is a performance upgrade for the BMW 3-Series E46 RWD. It is designed to improve the handling and ride comfort of the vehicle by providing improved damping and responsiveness. The FSD (Frequency Selective Damping) technology allows the shock to adjust to the road conditions, providing the driver with a more comfortable ride. The shock is constructed with a high-quality steel body and a corrosion-resistant finish for long-lasting performance.