This SES Suspension Upgrade fits the front suspension of a Chevrolet Silverado 2500HD/3500HD & GMC Sierra 2500/3500 truck. Our hollow rubber springs are engineered to deliver a progressive spring rate. In other words, the more weight that pushes down on the rubber springs (weight from a snowplow or heavy aftermarket accessories - such as a steel bumper) the harder they work to prevent front-end sag. This product ships in approximately 1 days