The item is a flight safety critical aircraft part (fscap)
A nut having 6 flat sides and an integral washer which extends beyond the flats or periphery. An integral feature is incorporated for locking on the threads of a mating member.
Classification: Nuts of iron or steel
NSN 6220-01-123-5139
NSN 4140-01-394-5655
NSN 5835-01-495-0595
NSN 4140-01-254-2739
NSN 6150-01-149-0515
NSN 6145-00-578-7522
NSN 5935-01-556-2466
NSN 5930-00-186-2442
NSN 6650-00-409-6578
NSN 5905-01-277-2581
NSN 6105-00-305-7727
NSN 5935-00-111-0509