BBK 2.5 inch Off-Road H-Pipe for Ford Mustang GT/Cobra for all BBK direct replacement H-pipes feature a 2.5 inch diameter CNC mandrel bent aluminized tubing to ensure maximum flow and horsepower. OEM original 02 sensor locations and factory style die-stamped flanges ensure a perfect fit. BBK in-house dyno testing has shown gains of 15-20 horsepower depending on the application. All BBK full-length H-pipes are designed as a direct bolt on to factory headers or any aftermarket shorty headers.