For Subaru Impreza WRX 4.5" Muffler Tip Catback+2-PC Header+Downpipe - GD GG EJ20 EJ25 Made of High Quality T-304 Stainless Steel Material; TIG Welded CNC Machine Flange Increase Engine Output and Efficiency; Instantly Gains Up to 10 - 15 Hp./Tq. Catback - Muffler Tip Type: Rounded Tip / Tip Diameter: 4.5" / Inlet Size: 3" / Removable Silencer Included Header - O2 Sensor Bung Insertion / Metal Gasket Included / Inlet: 1.5" / Outlet: 2" Downpipe - Inlet Size: 4.375" x 2.25" (Oval) / Outlet Size: 3" / Piping Diameter: 3" / O2 Sensor Bung and Flex Pipe Insertion