Chevy, Big Block Down and Forward Turbo Headers. All tubes are CNC mandrel bent for optimal flow. Made from 304 stainless steel for maximum corrosion resistance. Starting with a CNC cut 3/8" thick flanges into 2-1/4" diameter primaries, Flow into 4" slip-fit collectors. Headers are fully TIG welded and back purged. Mill finish, These, are TIG welded for strength and durability. These kits come with a lifetime warranty and proudly made in the USA.