ICON's 4.5" Stage 6 System is comprised of 4.5” lift coil springs optimized for trucks equipped with gasoline engines with a dual rate design that allows for a softer initial rate for superb on-road comfort and a firmer secondary rate that increases during compression for excellent bottoming resistance and off-road performance. ICON Vehicle Dynamics Ford Super Duty 4-Link kit further improves performance by eliminating suspension bind commonly experienced with factory radius arms during articulation and allows on-vehicle caster angle adjustment. This “freeing up” of the front end and the ability of the 4-Link Kit to maintain positive caster through the range of travel equates to an unparalleled ride quality in all conditions. The fabricated track bar drop bracket allows the axle to be properly centered under the frame and reduces road feedback throughout the steering system with improved on- and off-road manners thanks to the elimination of bump steer. An adjustable track bar allows for on-vehicle adjustment to fine tune track alignment as well as eliminating the deflective OE track bar bushings for an overall more rigid unit to improve the vehicles handling characteristics.