Fitment Information May also be used in the fabrication of custom exhaust systems (see measurements below). Does not fit 2.5" Mustang or GTO systems. MEASUREMENTS: 3" ID/OD 4" body diameter 18-1/4" overall length Product Description Get maximum flexibility from your modular SLP cat-back exhaust system with this "Shotgun" Race Resonator. It allows you to switch between muffled and "wide open" exhaust configurations in a matter of minutes. Each resonator is constructed from hand-polished stainless steel and embossed with the classic SLP logo.