This SES suspension upgrade fits your RV trailer suspension with an underslung axle setup and a leaf pack width less than 2.25 inches. Each laser cut piece of steel is precision bent and powder-coated to ensure a quality fit. What makes Timbren SES kits different from other suspension enhancement systems? Unlike air bags, our kits require zero post-installation maintenance. And unlike other systems, you can install and haul in under 30 minutes, right from your driveway.