aFe's Twisted Steel headers outflow and outperform the Ford diesel factory exhaust manifolds for a true, bolt-on performance header system. These precision-designed, hand-crafted headers are mandrel-bent from 1-3/4" into 2" heavy duty gauge .120" wall, brushed finish 304 stainless steel tubing and are 100% hand TIG-welded for strength and durability. Optimized tube lengths deliver true pulse control technology for improved flow and performance across the power band. Laser-cut, heavy duty head flanges are machined to match the exhaust ports for a secure seal. EGT ports with plugs, quality hardware and gaskets are included to ensure hassle-free installation and quality fit. Performance Gains: Outflows factory manifolds by up to 7%. Brushed Finish 304 Stainless Steel Construction: Constructed of brushed finish .120" wall, 1-3/4" into 2" mandrel-bent 304 stainless steel tubing for strength and durability. Optimized Tube Lengths: Tube lengths and mitered collectors are optimized for true pulse control technology which improves flow and performance across the power band. Heavy Duty Flanges: These headers incorporate laser-cut, heavy duty flanges machined to match the exhaust ports for a direct-bolt on, leak-free seal. EGT Ports: Two 1/8" NPT exhaust gas temperature (EGT) ports are incorporated. This allows for easy installation of sensors, gauges or testing equipment. TIG-Welded: 100% TIG-welded for strength and durability. All aFe exhaust systems are engineered and manufactured in our Corona, California manufacturing facility.