BBK 1698 2-3/4" High Flow Performance Full X-Pipe with High Flow Catalytic Converters for Shelby Mustang GT500 BBK is your Number One Aftermarket Performance Exhaust Brand in the USA - American Designed and Built BBK Hi Flow X Pipes are Built with CNC Mandrel Bent Tubing for 35% Increased Flow Over Stock to Increase Horsepower, Torque and Performance 2.5 Inch Full Length X Pipe with Hi Flow 49 State Legal Catalytic Converters Fits all Stock and Aftermarket Shorty Exhaust Headers Bolt on Additional 12-20 Horsepower and More Aggressive Sound, OEM Style Dome Connections for Easy Fitment These BBK Hi Flow Exhaust X Pipes Fit all 2007-2013 Ford Mustang Shelby Gt500 Applications - Aluminized Steel