Downpipe designed for: Audi A3 TT 1.8T VW Golf IV Polo Bora 1.8T Downpipe by TurboWorks, made of 100% stainless steel. Inlet / outlet diameter (internal): 63 mm Outer diameter of the system: 64 mm Downpipe intended for: Audi A3 TT 1.8T VW Golf IV Polo Bora 1.8T The downpipe by TurboWorks, is made of 100% stainless steel. Inlet / outlet diameter: 63mm