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 5920-01-010-6537
NSN 5960-01-120-6523
NSN 5960-01-658-9538
NSN 6105-01-202-9339
NSN 6320-00-433-2773
NSN 5945-00-829-3297
NSN 6685-01-193-1733
NSN 4140-01-106-1652
NSN 5985-01-147-2862
NSN 6130-01-464-3341
NSN 5985-01-012-6941
NSN 5945-01-502-9531