All Skyjacker® systems for the Jeep Wrangler JL 4-Door 4WD features DUAL RATE-LONG TRAVEL coil springs to ensure superb highway ride quality and performance on rough terrain - whether it's the streets you travel or when hitting the trails. The DUAL RATE-LONG TRAVEL coil springs offer the best of both driving worlds! What this means is the 1st spring rate offers an exceptional highway ride AND the coils will expand while off-roading during extreme articulation as the suspension droops to keep the tires in contact with the ground much longer than a linear rate, or single rate, coil spring resulting in a smoother & more controlled ride while keeping the coil in the coil bucket at full droop. The 2nd rate (lower coils) only engage after compression past the 1st rate. This second rate allows consistent control and stability when heavy off-road suspension movement is required.