Hooker's Corvette Side Mount Headers are built form lightweight 18 gauge tubing. 4" Side-tubes slip directly onto the collector for a leak free seal. Each Hooker Super Comp Corvette Side Pipe Exhaust Systems include Hooker's 4" Glass-pack muffler inserts (612-750). This Corvette Side Exhaust System includes Hooker's Metallic Ceramic Thermal Barrier Coating in addition to all hardware necessary to complete installation.