2001-2004 Duramax LB7 BD Diesel Up-Pipe Kit (1043800)2001 2004 GMC Chevy Duramax 6. 6L LB7 BD's Duramax up pipe kit uses 304L 2 inch stainless tubing which prevents loss of heat energy and will not corrode like aluminized steel or 409 stainless. Must have aftermarket downpipe will not fit OEM down pipe. 304 stainless steel precision cast mounting flanges eliminate exhaust tubing blowouts and ensures correct fitment 304L 2 inch stainless tubing prevents loss of heat energy and will not corrode like