Silverado & Sierra Longtube Headers 1999-2006 (4.8L, 5.3L, 6.0L Engines) 1 7/8" Primaries Mandrel Bent Tubing, CNC Machined Flanges Race Version, 304 Polished Stainless Steel 1 7/8" Primaries, Standard Graphite Manifold Gaskets 1999-2006 (2wd & 4wd) Gains over 25rwhp