2003-11 Crown Vic / Grand Marquis 4.6L 2V 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 1-5/8″ primaries, 3″ 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.