Borla 21-23 Ford Tremor 3.5L V6 AT 4WD 4DR CC SB 3in ATAK Mid-Section ExhaustThis Mid Section features 3" diameter pipes and the aggressive ATAK(r) sound. It fits with either the O. E. tail pipes or BORLA tail pipes 60640, 60640BC, or 60640CFBA. It features our Polyphonic Harmonizer and SwitchFire(tm) technology. BORLA(r)'S Polyphonic Harmonizer Technology utilizes patented units that contain pipes of different diameters and lengths to create multiple exhaust notes that harmonize to deliver a clean, rich, full bodied sound.