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 5998-01-188-6410
NSN 5975-01-483-1515
NSN 6610-01-288-6103
NSN 5999-01-487-3564
NSN 6650-01-087-8993
NSN 2925-00-275-1807
NSN 6135-00-080-9176
NSN 6135-01-222-0703
NSN 6620-00-226-2285
NSN 6145-01-422-3006
NSN 5990-00-892-5537
NSN 6110-01-476-6463