Axle-Backs #11376 and #11579 convert your '84-'91 Corvette from the stock 2.25" system to a more aggressive, 2.5" system. To complete this conversion you will need to order a "Y-Pipe" assembly, either a #60001 for the '84-'85 or the #60002 for '86-'91. BORLA Cat-Back and Axle-Back exhaust systems feature patented straight-through and multi-core technology to unleash hidden horsepower. Increased exhaust velocity adds power, driving excitement, fuel economy, and the distinctive BORLA Sound of Power respected by motoring enthusiasts everywhere. Each system is built from premium, high-quality T-304 austenitic 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-controlled CNC manufacturing ensures an accurate fit. Best of all, BORLA 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.