For Nissan Altima 5.75" x 3" Oval Muffler Tip Catback+Manifold Header Exhaust System - QR25DE 4Cyl Application: 02-06 Nissan Altima 4-Cylinder Catback - 5.75" x 3" Oval Muffler Tip / Inlet Size: 2.25" Header - Inlet: 2"x1.25" (Rectangular) / Outlet: 2.5" / O2 Sensor Bung Insertion / Metal Gasket Included TIG Welded CNC Machine Flange for Resistance Against Pressure and Corrosion Dyno Proven Increases Low End Torque and Horse Powers; Instantly Gains up to 10 - 15 Hp. / Tq.