This low-profile UNF hex nut is a machined jam nut manufactured to ASME B18.2.2 standards, made from free-cutting steel with an electrolytic zinc plating. Thanks to its low-profile design and 040 strength class, the nut has a reduced load capacity and is primarily used to keep other nuts from vibrating loose. It features Unified National Fine (UNF) threads. The electrolytic zinc coating makes it suitable for indoor use or applications with very mild exposure.