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 6220-01-361-9152
NSN 6610-01-201-7943
NSN 5985-01-118-8509
NSN 6650-01-383-4526
NSN 6130-01-524-3058
NSN 6110-00-371-2458
NSN 6105-00-978-2292
NSN 5905-00-403-5793
NSN 5965-01-390-9240
NSN 5990-01-224-8052
NSN 6645-00-012-5834
NSN 6145-01-431-2262