GHL's Golf/GTI Thru-Flow™ cat back exhaust is a 304 stainless steel, mandrel bent system. Our exhuast begins after the factory catylic converter with a 3" center pipe which contains a small 4" resonator. The 3" pipe continues to the back to the muffler and two dual inch 3" round rolled tips. With TIG welding, fully stainless construction, and CNC hangers, you will not find a higher quality system on the market.