Carli HD Full Replacement Leaf Springs are intended for trucks with constant 1,000 pounds in the bed. Designed for work trucks with heavy duty toolboxes or any rig with 1,000 pounds in the bed. This is NOT a leaf spring pack designed to run unloaded, it requires the 1,000-pound load to sit at the intended height and function properly. Being a far heavier spring rate than the Carli standard leaf spring AND designed to operate with a much higher center of gravity, we recommend Carli 2.5″ remote reservoir shocks and custom shock valving for optimal control and ride quality.