The revolutionary new Zone 4" system features new front coil springs that are designed to not only ride great, but will hold up over the long haul. A 1-1/2" solid steel track bar is included to properly center the axle after lifting. This track bar features new oversized, high-durometer urethane bushings for long term performance. The shocks were custom valved to work perfectly with the new Zone coil springs to increase off road performance while still offering unmatched on road ride quality. The rear kit comes with 5" blocks to replace your factory blocks so there is not stacking of blocks when you are in the Zone. This reduces rear axle wrap compared to other similar systems on the market. With the front replacement track bar and the rear block kit, this system is one of the easiest installations on the market for a 4" system.