For the person looking for a complete Header-back dual exhaust system with an aggressive tone. With easy fit in mind, Flowmaster's American Thunder system for GM F-Body cars include specially-selected 50 series slim-line mufflers to make your Camaro or Firebird come alive. This Header-back dual exhaust system uses 2.50 in. 409S stainless steel tubing (backed by our lifetime limited warranty!) and a durable H-pipe design that delivers improved throttle response, power and mileage. American Thunder systems deliver a moderate to aggressive interior and exterior tone and are suited to the enthusiast who wants their performance 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. Note 1- Off Road racing use only - not legal for use on catalyst equipped vehicles. Note 2- requires double hump crosspipe. Note 3- requires fabrication and/or welding to adapt system to manifolds or headers.