2, ASME B1.Size: 1/4 inch-20Most commonly used and versatile nutFinished nuts are six sided nuts of standard thickness vs heavy duty hex nutsScrews onto a bolt, cap screw or threaded rod of the same thread sizeUse with washers to help distribute the load (not included)Thread Type: Coarse, Thread Class: UNC-2ASpecification(s) Met: ASME B18.2.1 & ASTM F467.
2. They are ideal for use on decks since installation can be accomplished without having access to both ends of the fastener, as opposed to standard hex bolts that require a nut on the opposite end.