These are constructed out of 304 stainless steel mandrel bent tubing with 1020 CRS laser cut flanges. The oxygen sensor bungs have been relocated to solve the problem of breaking them when you car is lowered. It is impossible to break them anymore with the revised mounting locations. The High Flow Cat version uses a Magnaflow Ceramic Core Catalyst which is also stainless steel. Everything is TIG welded for superior quality. There is also a two piece combo that includes a 2.5″ flex pipe made from stainless steel with a v-band connection. These are custom made to order at this time. Lead time varies depending on production.