The proven race design of the Pro series mufflers from Flowmaster delivers performance equal to and surpassing open-pipe systems. From street trucks to diesel "pullers" to every class of dirt or asphalt racing, the performance of these Pro series mufflers is matched only by their ability to dramatically reduce sound levels across the rpm range. Flowmaster mufflers offer 409 stainless steel internal construction enclosed in a durable, fully welded, 18-gauge aluminized steel case. Master the flow of your diesel system like a pro with Flowmaster Pro series mufflers.