MILLTEK SSXAU737 Cat-back Quad 100mm GT100 AUDI S6 4.0 TFSI C7 quattroDescription MILLTEK SSXAU737 Cat back Quad 100mm GT100 AUDI S6 4. 0 TFSI C7 quattro The Cat Back systems are designed as direct replacements for the original exhaust system, offering improved sound and aesthetics. Multiple configurations are available, allowing the owner to select the desired increase in exhaust volume or a more aggressive tone. Each system is manufactured from 304L aircraft grade stainless steel, ensuring durability under harsh