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