These custom long automotive hex flange bolts were manufactured for our customer to Grade 10.9 specifications with black zinc finish. 100MM of M13-1.75MM thread was rolled behind a 84MM unthreaded shoulder. The flange diameter was set to 50MM and the hex above to 19MM across the flats. Black zinc finish is good for corrosion resistance but is always cosmetically tricky due to the imperfections you get on the surface from the bake process, as well as the tumbling of large parts during packaging and transport.