Invidia (HS15STIG3T) Q300 Rolled Titanium Quad Tip Cat-Back Exhaust System for Subaru WRX/STI Fits 2015-Up Subaru WRX/STI 4 Door Pipe size: 76mm (3"), Tip size: 110mm (4.3") Constructed with high-quality SUS304 stainless steel, CNC-machined flanges, Robot TIG welding and double wall tips Flat bottom shaped muffler design results in improved high speed aerodynamic performance, providing greater horsepower, torque gains and a rich, deep, sporty sound Rolled, Titanium Quad tips