For Nissan Altima 2.4 U13/L30 Stainless Steel 4-1 Header Exhaust Manifold Made of High Quality T304 Stainless Steel Material TIG Welded CNC Machine Flange Increase High Flow Air, Instantly Gain 10 -15 Hp. / Tq. 4-1 Design / O2 Sensor Bung Insertion and Metal Gasket Included Inlet: 1.65" / Outlet: 2"