For Chevy/GMC GMT900 4.8-6.0 Stainless Steel 8-2-1 Long Tube Header/Exhaust Manifold+Y-Pipe Made of High Quality T-304 Stainless Steel with Computerized Mandrel-Bends for Strength and Durability i.e. Maximizing Smoothest High Exhaust Air Flow Rate 8-2-1 High Performance Racing Spec. Design, Produces the Most Top End Power Offers the Best Flow Characteristics for the Engine at High Engine Speeds Increase High Flow Air, Instantly Gain 10 -15 Hp. / Tq. Inlet: 2"(OD, 8 Ports) / Outlet: 3"(OD) / 10mm Thick Header Flange / 16 Gauge Wall Piping / O2 Sensor Bung and Metal Gaskets Included