Timbren SES kits are designed to work on vehicles with factory ride height, allowing for a 1 inch space between the Aeon(r) rubber spring and your vehicle's suspension when unloaded. But if you have a leveling kit, body lift, or full suspension lift, the increased distance can reduce the performance of your SES kit. However, there is a way you can still enjoy a level, controlled towing experience with your lifted truck. How? Timbren SES spacer kits reduce the gap between the Aeon(r) rubber spring of an SES kit and the increased distance between your lifted pickup's frame and rear axle - enabling your Timbren SES kit to perform properly. Each spacer kit comes with two 1 inch and two 1/2 inch spacers, along with necessary hardware - so you can mix and match the spacers to achieve desired height.