DNA Motoring HDCHC01DX Stainless Steel Exhaust Header Manifold [For 01-05 Honda Civic DX/LX] Made of high quality steel covered with metallic ceramic coating.with 4-1 direct bolt-on design TIG welded CNC machine flange O2 sensor and EGR bung insertion / Metal gasket included / Inlet: 1.5" / Outlet: 2" Increase high flow air, instantly gain 10 to 15 Hp. / Tq Application: Please check part finder on top of the page (Professional Installer is Highly Recommended) (No Instruction Included)