Big Block Chevy 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 2-1/2" Primaries and 4" Slip-Fit Collectors. Headers are fully TIG welded and back purged. These are TIG welded for strength and durability. These kits come with a lifetime warranty and proudly made in the USA.