This ad is a set of 9 vintage automotive OEM fasteners, specifically designed for the cylinder head of an engine of a vehicle from around the mid 1960's to late 1970's. The SAE grade 8 fasteners are a 4 1/2 inches in length and have a UNC 1/2 x 13 TPI, and the 6-point hex head is 3/4 inch. They are made in the United States and have a black oxide surface finish. These fasteners are not modified and come with a free return warranty. Although they are designed for a specific motor block, they are a rare find for collectors and enthusiasts and will also work for fixes that are not as extensive or technical as automotive repair.