This an exhaust manifold kit for mounting stock manifolds to the heads on your big block Chevy V-8 engine. These bolts are grade 8 stainless steel and are 1 1/4 inches long. These are ARP bolts and come with a polished finish. These bolts will withstand the high temperatures of the exhaust manifolds. We also include extra thick flat washers. They are for the engines that use all 3/8 bolts in the heads. Please verify the fit to your engine before ordering. These bolts are much stronger than the stock bolts and are rated at 170,000 psi.