it is Patented Bolt-on Design, silent Ride Polyurethane Stability Blocks, Plated And Powder Coated Components And Easy To Follow Installation Instructions Make This The Helper Spring Of Choice For Do It Yourself And Professionals Alike. Manufactured With Heat Treated Alloy Spring Steel In Our California Based Facility, These Units Increase Your Vehicles Level Load Carrying Capacity Up To The manufacturer Gross Vehicle Weight Rating. With Its Progressive Rate Design This Helper Spring System Enables Trucks And Vans To Carry Loads With More Control And Stability. As Your Load Increases This Spring Automatically Increases Its Rate To Resist Sagging And Tail Dragging.

Product Features:

• Progressive Rate Leaves Do Not Effect Ride When Unloaded
• Never Needs Adjusting
• Load And Sway Control In One Spring
• Heavy Duty Plated Hardware
• Simple Bolt On Installation