These 5 inch rear springs are progressively rated to improve the ride quality of your Ford Super Duty F250 / F350 truck, as well as increased performance. The multi leaf construction ensures a smooth ride with less chance of spring fatigue under load minimizing sagging. The bottom 3 leaves of the pack are flat to provide a secondary rate preventing harsh bottom outs and smooth transition through the suspension cycle. ICON 2.0 Aluminum Series or 2.5 Series Vehicle Specific tuned shocks recommended for best ride quality on or off-road.