The internal construction of Pro Series mufflers is T409 stainless steel and the outer case is fabricated from rugged 18-gauge aluminized steel. Pro Series mufflers consistently deliverer performance that is equal to or surpasses open pipe systems, while dramatically reducing sound levels across the RPM range. These round-cased mufflers deliver ground breaking sound control while delivering maximum power and exhaust system efficiency. The Pro Series mufflers work on all applications ranging from street trucks, diesel ''pullers'' and RV ''pushers'' to every class of racing on dirt or asphalt.