CNC Mandrel-bent tubes provide consistent tubing diameters for smooth flow and increases the cylinder scavenging effect and improves engine breathing Heavy duty 16-gauge 304SS (Polished Finish Only) and 409SS (Natural, Black Painted, and Ceramic Coated finishes) tubing for increased strength and durability 1-3/4†and 1-7/8†tubing diameters available for increased exhaust flow increasing performance and improved throttle response 3†collector for maximum strength and exhaust flow 7/16†thick header flange for a leak-free seal and maximum strength Premium aluminum header gaskets included 3†V-Band Flanges and Clamps are included Available in a total of four finishes (Natural, Black Painted, Ceramic Coated, and Polished)