Kooks Custom Headers - 06-11 Charger/09-11 Challenger - 6.1L HEMI Cat-Back System Kooks Cat-Back Exhaust. Made in entirely 304 Grade Stainless Steel, this system will make your HEMI scream. Match it with the Kooks Header system and watch out, this isn't your Grandma's 4 door sedan. Tube 3” Coll 0” Inlet 2 3/4" Outlet 3"