For Civic/Integra/Del Sol K20 Swap Engine Stainless Steel 4-2-1 Tri-Y Header/Exhaust Tubular Manifold 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 4-2-1 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: 1.9" / Outlet: 2.5" / O2 Sensor Bung and Metal Gaskets Included / 2.5" Inlet Cat or Test Pipe Required for Install