The CTS Turbo MK5 GLI 3" cat-back exhaust system is hand tig welded using the finest T304 stainless steel. Other MK5 GLI exhausts that are currently available can choke peak power and limit the breathing due to their 2.5" construction. The 3" design of the CTS Turbo MK5 GLI cat-back is ideal those of us chasing serious horsepower.