The Bilstein 17-21 BMW 530i B4 OE Replacement Shock Absorber - Rear is an original equipment direct replacement shock absorber for the BMW 530i. It is designed to provide superior ride quality, performance and durability. It features a monotube design that is gas-pressurized to provide consistent damping force and a self-adjusting deflective disc valving system to ensure optimal performance. It also comes with a limited lifetime warranty for added peace of mind.