These over axle pipes are recommended to be used with the BORLA® Axle-Back system and “X” Pipe to complete a Cat-Back™ system. Built from premium T-304 stainless steel, superior to T-400 series (such as 409), to give you the absolute best in performance and durability. Ultra-smooth mandrel bends ensure maximum flow & power, and precision computer-controlled CNC manufacturing ensures an accurate fit.