Stainless Works Headers 1-5/8" With Catted Leads (4WD Only) Factory Connect2004 08 Ford F 150 4. 6L 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 with hi flow catalytic converters, 2 1 2" lead pipes and clamps. Designed to mate to factory connection point. Headers are fully TIG welded and back purged. These are TIG welded for strength and durability. These kits come with a lifetime