Flowmaster Exhaust 1999-2004 Mustang GT - Stainless Steel Cat-back Exhaust System 409S - American Thunder - Moderate Sound For the person who is looking for a complete cat-back dual exhaust system with an aggressive tone. With easy fit in mind, these systems are mandrel bent for maximum performance and include specially selected mufflers. American Thunder? These systems deliver a moderate to aggressive interior and exterior tone and are suited to the enthusiast who wants their perfomance to be heard. Like all Flowmaster systems, the benefits include improved throttle response, power and mileage. Designed for an easy fit, these systems include all necessary parts and hardware for easy installation. Fits: 2001 FORD MUSTANG BULLITT V8 4.6 GAS FI 1999 - 2004 FORD MUSTANG GT V8 4.6 GAS FI 2003 - 2004 FORD MUSTANG MACH 1 V8 4.6 GAS FI Material: Stainless Steel Inlet: 2.50 in Outlet: 2.50 in