The Koni Special Active Shock FSD 12-17 BMW 2/3/4 Series RWD w/ M-Technik Susp Rear is an advanced shock absorber designed to provide superior handling and ride comfort. It features Koni's Frequency Selective Damping (FSD) technology, which automatically adjusts the damping force based on the frequency of the road surface. The shock is designed for BMW 2/3/4 Series RWD vehicles with M-Technik Suspension Rear and is constructed from high-quality materials for long-lasting performance. It offers improved road handling and stability, as well as improved ride comfort and control.