APR's A4 Exhaust is a stainless steel, 2.5" mandrel bent, cat-back exhaust. On an A4, the catalytic converter is bolted to the turbocharger and then the exhaust begins with the downpipe. Unlike most other aftermarket exhausts, the APR exhaust includes a downpipe. This exhaust is very quiet and simply changes the tone of the exhaust to a deep, unobtrusive sound. With TIG welding, fully stainless construction, and CNC'ed hangers, you will not find a higher quality system on the market.