The Bilstein B6 2001 BMW M3 Base Rear 36mm Monotube Shock Absorber is a high-performance shock absorber designed for the 2001 BMW M3. It features a single-tube design and a 36mm diameter, which allows for increased oil capacity and a consistent fade-free performance. The shock absorber also has a high-pressure gas-charged design that helps to provide a more comfortable ride, as well as improved handling and braking. Additionally, the shock absorber is corrosion-resistant and comes with a limited lifetime warranty.