APR's cat-back exhaust is a stainless steel, mandrel bent system. Thier cat-back exhaust begins after the factory catalytic converter with a with a 3.0" center pipe which contains a small 4" resonator. The 3.0" pipe continues back to the polished muffler and then to the polished tip or tips depending on your vehicle. With TIG welding, fully stainless construction, and CNC'ed hangers, you will not find a higher quality system on the market.