Cobb Tuning Subaru SS 3" Cat-Back Exhaust WRX Hatch 2011-2014, STI Hatch 2008-2014 - 515101EMISSIONS This part is not an emissions related part and therefore can be used on Emission Controlled Vehicles. DESCRIPTION Exhaust gasses are guided through 3 inch diameter tubing into the center inlet of the fully 24 inch wide muffler section. Internal to the muffler, the exhaust gasses pass through a reversed Y merge, efficiently splitting the exhaust into separate muffling chambers on each side of the canister. 2. 5 inch outlets emerge