TeraFlex JL 4dr: Lift Coil Springs are perfectly engineered for your 4-door JL Jeep Wrangler Unlimited. Our engineers focused on extensive rate tuning and dynamic balance between front and rear and side-to-side load bias to produce Lift Coil Springs that deliver unsurpassed highway handling and off-road performance. Up front, we chose progressive dual-rate lift coil springs that provide optimal performance both on and off road. These progressive dual-rate coil springs provide consistent performance and predictable handling throughout normal street driving – just like a linear rate spring. When the axle begins to droop, the softer sprung upper section of the coil spring begins to unwind for maximum flex and spring retention. We recommend pairing TeraFlex Lift Coil Springs with Falcon Performance Shocks for superior performance. TeraFlex coil springs and Falcon shock absorbers have been engineered together to improve both compression and rebound for optimal vehicle stability.