Hex Nuts Grade 2 Zinc NC Zinc plated to meet ASTM Specification B633, Class SC4, Type 1. Used in conjunction with low carbon bolts and screws that are not treated.
5/8 inch Jam Nut - Coarse - Grade 2 Unalloyed steel may be surface treated for corrosion resistance and other properties Second nut threaded over a bolt to prevent the first from loosening