This 2.5" diameter Axle-Back system features the aggressive ATAK(r) sound with no drone inside the vehicle. The exhaust exits through single 4" round black chrome on T-304 stainless steel tips. on each muffler Using Borla(r) Stainless Steel Polish p# 21499 is NOT recommended with these black chrome tips. We suggest cleaning the tips with hot water and a microfiber cloth. A system with bright chrome on T-304 stainless steel tips is also available. By adding Borla(r) X-Pipe with Mid-Pipes part number 60705 you can create a Cat-Back(tm) system for your Mustang GT. Borla(r) Cat-Back(tm) and Axle-Back exhaust systems feature patented straight-through and multi-core technology designed to unleash hidden horsepower. Increased exhaust velocity adds power, driving excitement, fuel economy, and the distinctive Borla(r) Sound of Power respected by motoring enthusiasts everywhere. Each system is built from premium T-304 stainless steel, superior to T-400 series knockoffs (such as 409), to give you the absolute best in performance and durability. Ultra-smooth mandrel bends ensure maximum flow & power, and precision computer numerical control (CNC) manufacturing ensures an accurate fit. Best of all, Borla(r) stands behind every system with a Million-Mile Warranty. Just what you'd expect from the world's most experienced (and most winning) exhaust brand.