The Rubicon Express 3.5 in. Super-Flex Progressive Coil Lift Kit For The JK Owner Who Wants A More Affordable Price. The Lower Control Arms Of Your JK S Suspension Are Upgraded w. Our Super-Flex Front Control Arms While The Stock Upper Control Arms Are Retained. The 3.5 in. Super-Flex Kit Will Improve The Trail Flexibility Of Your JK While Retaining A Comfortable Street Ride.