US / Inch - Grade 5 Finished Hex Nuts. These are standard Hex Nuts (also called Finished Hex Nuts) that are made from Medium Carbon Zinc-plated Steel (RoHS compliant Cr+3 zinc).
Nut Size is the size of the screw that the nut is for (Example: 1/4"-20 nut for a 1/4"-20 screw).