For the person who wants a subtle custom appearance with all the benefits that a Flowmaster cat-back exhaust system provides, S.O.S. (Single Out Side) systems are the perfect choice. American Thunder 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 are improved throttle response, power, and mileage. All necessary parts and hardware included for easy installation.