For Ford Mustang GT 4.6L 3.75" Dual Muffler Tip Catback+Header+Y-Pipe Exhaust System - 5th Gen FR Dyno Proven to Instantly Increases 15 -25 Horsepower/ Low End Torque; Increase Engine Output and Efficiency TIG Welded CNC Machine Flange for Resistance against Pressure and Corrosion Aggressive Deep Sound while Ensures Smooth Exhaust Gas Flow Catback: Inlet/ Muffler Exhaust Tips: 2.5"/ 2 X 3.75"OD (Slanted); Main Piping Diameter: 2.5" Header: Inlet / Outlet: 1.75" / 2.5"; 2 x 4-1 Manifolds Connecting into a 2.5" Y-Pipe; O2 sensor bung insertion; Metal gasket included