This spring is from their "Reinforced Coil Suspension Auxiliary Spring Kit" product line. The MAD Auxiliary springs are fitted in or next to the existing main spring. They only come into action when the load reaches a certain load level. In other words, when the main spring is no longer capable of handling the increased load. The auxiliary spring provides the required extra capacity when this happens. A spring that works in this way is referred to as a progressive spring. Auxiliary springs are easy to fit in most cases.MAD coil springs are high-quality components and approved by T?V and RDW. This means that they meet the highest international automotive standards. This kit is specific to the Dodge Ramp Promaster 3500 (double leaf spring). Van manufactured from 2014 to current.