This SES Suspension Upgrade fits the rear suspension of a Chevrolet Silverado 1500 and GMC Sierra 1500 pickup truck. Each laser cut piece of steel is precision bent and powder-coated to ensure a quality fit. We’ve engineered our hollow rubber springs to deliver a progressive spring rate. In other words, the more weight that pushes down on the rubber springs the harder they work to prevent rear end sag. Whether you’re pulling a trailer or carrying a heavy load in the bed of your truck, our hollow rubber springs adjust automatically to keep the vehicle level at all times. We designed each SES Suspension Upgrade to provide superb ride quality – loaded or unloaded. (There should be a 1/2 Inch to 1-1/2 Inch gap between rubber spring and axle to ensure unloaded ride quality.) Unlike other auxiliary spring systems, the SES Suspension Upgrade guarantees the best of both worlds.