Cobb Tuning's catted downpipes for the 05-09 Legacy GT use 3" bellmouths that scale to the stock 2.5" size piping where they connect to the mid-pipe. The Cobb downpipes are designed to bolt to any stock or 3" aftermarket catback exhaust. A factory style donut gasket attaches the downpipes to your catback. All Cobb downpipes feature a unique, cast bellmouth and an oxygen sensor bung close to the turbo that will come in handy when you want to run on the dyno with a dedicated wideband sensor.