The Load Pro 35 kit is designed for the E450 motorhome Super Duty with leaf springs of an 11 leaf stack or more. The kit contains 2 heavy duty black powder coated leaf assemblies that run over both sides of the axle. * Necessary Mounting Hardware Included or Listed Above Hellwig's steel leaf helper springs are ideal for helping manage your load more efficiently. Provided the vehicle can be lifted, they are easy to install bolting on to your new or old factory rear leaf springs and require little or no maintenance.