This commonly-used term was actually originated by Borla, who pioneered the concept. "Cat" is motorhead sh"rthand for "Catalytic Converter." A Borla Cat-Back exhaust replaces your entire stock system from the catalytic converters "back” to the tips ex"ting the bumper. This type of system delivers the most dramatic upgrade in sound, because it includes improvements to virtually all the undercar piping, incorporating Borla’s ultra-smooth mandrel bends, X-Pipe technologies, pipe diameter specs and other characteristics that shape the sound. Borla Cat-Back systems are available for a wide variety of popular cars and trucks, and are offered in your choice of sound technologies — ATAK, S-Type and Touring — each with their own distinct volume and character.