For Honda Civic 4-1 Design Stainless Steel Exhaust Header Kit (Black Ceramic Coated) - 7 Gen EM ES D17A2 Engine Made of high quality steel covered with metallic ceramic coating.with 4-1 direct bolt-on design TIG welded CNC machine flange O2 sensor bung insertion / Metal gasket included / Inlet: 1.5" / Outlet: 2.25" 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)