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 a 3.5" rolled edge tips. With TIG welding, fully stainless construction, and CNC hangers, you will not find a higher quality system on the market.