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 5930-01-528-7523
NSN 6240-01-476-7935
NSN 6130-00-643-4894
NSN 6145-00-146-2932
NSN 2925-01-418-8106
NSN 5910-01-633-9963
NSN 6610-01-224-7247
NSN 5990-01-063-2532
NSN 6685-00-832-6922
NSN 5915-00-733-0855
NSN 4140-01-100-7922
NSN 5999-00-578-7488