Custom Hex Bolt Introduction Countersunk hex head bolts are made of iron and stainless steel bolts. The production grades of iron are 4.8 bolts, 8.8 bolts, 10.9 bolts, and 12.9 bolts. Stainless steel bolts are divided into stainless steel SUS201 bolts, SUS304 bolts, and SUS316 bolts according to their materials. Not only is this bolt highly chemical and corrosion resistant, it is also extremely...