Size: 3/8 inch-16 Most commonly used and versatile nut Finished nuts are six sided nuts of standard thickness vs heavy duty hex nuts Screws onto a bolt, cap screw or threaded rod of the same thread size Use with washers to help distribute the load (not included) Thread Type: Coarse, Thread Class: UNC-2B Specification(s) Met: ASME B18.2.2 and ASTM A563 Gr A