For 66-87 Chevy/GMC SBC Truck Long Tube Stainless Steel Exhaust Headers Designed for 1966-1987 2wd and 4wd Chevy trucks with Small Block Chevy The diameter of heavy duty tube is 1 1/2" The thickness of flanges is 5/16" For the collector: the size on muffler side is 2 1/2";the size on tube side is 3" Comes with the left and right headers, all gaskets, bolts, and collectors with flanges as exactly described in the picture.