Designed for hard tuned, street driven vehicles, the PS Revolution's exhaust pressure activated "active valve" system provides the hardcore enthusiast with the best of both worlds. The retracting valve is engaged and disengaged based upon exhaust gas pressure. This revolutionary new muffler design allows high powered street cars to maintain a tolerable, and legal, exhaust note at idle and light throttle acceleration while completely disengaging during high throttle, high load situations. Never before has an exhaust system seamlessly fused the streetability of a stock exhaust system and the performance of a low restriction racing exhaust. Like all A'PEX exhaust systems, the PS Revolution features a high quality SUS 304 stainless steel muffler. Being the standard for performance and reliability, the PS Revolution uses full stainless steel mandrel bent piping for added strength and minimum weight.