DNA Motoring HDS-SBC-HIB32 Stainless Steel Exhaust Header Manifold Made of high quality Steel with 2 x 4-1 direct bolt-on design TIG welded CNC machine flange Metal gasket included/ inlet: 1.75"X1.5" (oval)/ outlet: 3.39" 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)