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. Best of all, BORLA stands behind every connection pipe with a Million-Mile Warranty. Just what you'd expect from the world's most experienced (and most winning) exhaust brand.