SLM Series 409 SS Turbo-Back Diesel Exhaust System (S6200SLM) by MBRP. Series: SLM Series. Exhaust Pipe Material: 409 SS. Exhaust Type: Turbo-Back. Main Piping Diameter: 4in.. Muffler Sound: Moderate. Exit Location: Single Rear Exit. CARB Compliant: Yes. Without Muffler. MBRP�s SLM Series is the ultimate in free-flowing exhaust systems, because they replace both the catalytic converter and any muffler in the stock system. MBRP�s SLM Series exhausts are made with tough T409 stainless steel, which will outlast your truck. T409 won�t take a mirror polish like T304, in fact it will show some minor surface corrosion after exposure to the elements. But rust through? Never. It�s the perfect metal for a working truck�s exhaust system; if you need a little bling just clamp a polished muffler tip on. Enjoy the improved performance and mileage afforded by these low-restriction systems for as long as you own your truck.