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 4140-01-139-6192
NSN 5910-01-016-8702
NSN 5975-01-119-3833
NSN 6145-01-555-8131
NSN 5965-01-580-0938
NSN 5965-01-467-1857
NSN 5895-01-501-1384
NSN 6150-00-192-2734
NSN 5960-00-917-5099
NSN 6240-00-682-8315
NSN 5950-00-755-2109
NSN 4140-01-289-0310