The FLO 618 is a 5" Cat-Back Exhaust system for the 2004.5-2007 Cummins 5.9L. It replaces your restrictive OE exhaust system with a 5" mandrel-bent exhaust system, this kit includes a high-flow muffler and is designed for street applications. Just like all of Flo-Pro's Exhaust kits, it will come with all the required clamps, pre-weld contour bent hangers, and stronger flanges to help you sail through the installation process. This exhaust not only sounds great, but will improve your torque, mileage, and throttle response!