Known for their phenomenal spring ride performance, Skyjackers precision engineering gives you all the vigorous off-road handling needed while providing the smooth street riding characteristics that you demand. Skyjacker specifically engineered a progressive variable rate coil spring, distinctively a 2-stage dual rate long travel coil. Spring rate progression is from a first Flex Rate to a second Ride Rate. First Flex Rate stage of coil spring delivers a comfortable ride with ability to flexexpand during full articulation as suspension drops (full droop). This keeps coil springs seated in upper coil mountbucket and tires in contact with terrain. Second Ride Rate stage only engages after compression past Flex Rate. Engineered with Wrangler’s distinctive suspension handling characteristics, rear coils are side specific. The process starts with 5160H chromium alloy material, an advanced method of shot peening and a presetting process. Each coil spring is blasted (shot peen) with hard steel pellets at very high velocities. Shot peening compresses the surface of the steel thereby increasing the tensile strength of the spring. Compressing the spring completely down to where the coils touch (solid height) is preset. This takes any fatigue or stress off the spring and eliminates sagging. Every coil spring has endured a cycle test to assure the very best in quality. A baked on powder coat provides an extremely durable protective barrier to prevent corrosion.