Two Axle-Back options are also available: an aggressive S-Type (PN 11750) and a more mellow Touring (PN 11752) – both replace only the over-the-axle pipes, mufflers and tips. BORLA®, the original pioneers of high-quality, T-304 austenitic stainless steel (superior to 409 or aluminized steel) free-flow exhaust utilizes patented award and race winning technology to deliver quality, sound, performance gains and enhanced fuel economy – all with an easy bolt-on installation. Best of all, each system comes with the unsurpassed BORLA® Million-Mile Warranty.