This Street I package is designed for the DIY hot rodders and is mission critical to improving your handling, by reducing unwanted and undesirable suspension movement . The rear end is loose because the sub-frame twists in the soft rubber Noise Vibration and Harshness (NVH) Voided sub-frame bushes , literally steering from the rear of the car. The inserts fill the NVH voids and do NOT require the OE bushes to be removed. The result is an IRS that tracks true and end to ?loose? rear end syndrome. The OE fluid filled radius bushes allow significant dynamic castor changes under load. The OE bushes have a soft rubber inserts. The EP6578 inserts are high durometer urethane and direct replacements. Pry out the soft OE rubber and insert the urethane. With a reduction in the compliance of the bush comes a direct reduction in dynamic castor change. The steering feel is more controlled. These are the essential upgrades for a 5th Gen Camaro. Pedders suspension components are addictive. They are street civil yet deliver amazing results on the track. If you never make another suspension upgrade, your 5th Gen will be much improved with no change in ride comfort. If you decide to build to add more later, the Street I is the perfect foundation for future upgrades.