The APR CB100018 VW MkIV R32 catback exhaust is a stainless steel, mandrel bent system. The APR exhaust begins after the factory catalytic converter with a 2.5" center pipe. This continues back to the single rear muffler that has two 4" dual wall tips. With TIG welding, fully stainless construction, and CNC'ed hangers, you will not find a higher quality system on the market.