The ST Coilover Kit 03-08 BMW Z4 (Z85) is a high-performance suspension system designed to improve the handling and ride of your BMW Z4. This kit includes a set of four adjustable coilovers with a threaded body and adjustable spring perch. It also features a monotube design and a progressive spring rate that provides a smooth and comfortable ride. The kit also includes all necessary hardware and instructions for installation. It is designed to lower the vehicle's center of gravity and increase responsiveness, allowing for improved cornering and overall handling.