70-74 Firebird/Trans Am: 350-455 Tube 1.75" x 28", Collector Size 3", Collector Length 10", Port Shape: Same As Port;Tuned-length primary tubes for maximum exhaust scavenging and velocity; All necessary hardware included for a complete installation; Designed for optimal performance; Industry’s best welds for durability; 5/16” machined flanges for a perfect seal; Long transition collector for decreased back pressure; Light weight & sturdy 18 gauge tubing; Mandrel-bent tubing for smooth exhaust flow;