Free up the flow of exhaust gas and gain both horsepower and torque in your Subaru with Invidia's easy to install catted downpipe with divorced bellmouth opening. Features: Installation Hardware Included 304 Stainless Steel Catalytic Converter 3" Pipe Diameter Invidia downpipes provide a very noticeable gain in horsepower and torque by freeing the flow of exhaust gas closest to the turbocharger or headers. Most Invidia downpipes features a large 4-in stainless-steel bellmouth and 3inch piping to enhance power by freeing excess gas. Each Invidia Downpipe can be bolted up to any Invidia Exhaust or a stock exhaust for an easy installation.