The Alpha Competition downpipes with decat are made from T304 stainless steel and feature 2.5" / 63.5mm mandrel-bent pipework. They are TIG welded for enhanced durability and fit directly from the turbos (RS4 / RS6 double flange) to the catback on Audi S4 B5 / RS4 B5 models.Seamless bolt-on fit f..