For Nissan Altima Performance 4-1 Design Stainless Steel Exhaust Header Kit (Polished Chrome) Application: 02-06 Nissan Altima 4-Cylinder Inlet: 2"x1.25" (Rectangular) / Outlet: 2.5" Made of High Quality T304 Stainless Steel for Strength & Durability Constructed with TIG Welded CNC Machine Flange for Percision & Fitment Comes with O2 Sensor Bung Insertion & Metal Gasket