|Mandrel-bent from 2 1/2 in. diameter, 16-gauge, aluminized steel tubing, this off-road X-pipe assembly delivers more power to your Mustang. It features an "X" style crossover design that helps exhaust pulses scavenge each cylinder better. The X-design is vastly superior in performance design that the H-style offering higher velocity of exhaust flow and improved torque and horsepower across the entire RPM range. Typical horsepower gains of 15-18hp are normal.