If you own a Jeep powered by the 4.0L I-6, you know that it is a solid dependable powerplant. Depending on what year vehicle you have, you may also know that it is short on power and torque and has a tendancy to crack exhaust manifolds. JBA has spent countless hours developing and testing the ultimate solution for these power and durability challenges. JBA's unique headers designes are crafted from the highest grade materials to ensure lasting performance for your Jeep. The head flange is a one-piece design that is CNC laser cut from 1/2" steel plate to guarantee a tight seal with the head. JBA's collector features a 3/8" flange secured with a 360 degree weld for maximum strength. Each kit includes high quality hardware and gaskets for a professional no-leak installation. Don't settle for low grade materials and inferior designs.