For Subaru WRX GD GG Turbo Stainless Steel 4" Rolled Tip Catback System+1pc Polished Exhaust Header Made of High Quality T-304 Stainless Steel with Computerized Mandrel-Bends for Strength and Durability TIG Welded CNC Machine Flange for Resistance Against Pressure and Corrosion Aggressive Deep and Smooth Tone Sound while Ensures Smooth Exhaust Gas Flow Catback - 4"(OD) Muffler Rolled Tip / 3"(ID) Inlet / 3"(ID) Main Piping / 14mm Thick Double Walled Muffler Tip Header - 4-1 Design / O2 Sensor Bung and Metal Gaskets Included / Inlet: 1.5" / Outlet: 2"