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 5895-01-167-8559
NSN 5915-01-023-2555
NSN 5950-00-575-9980
NSN 5960-00-171-9575
NSN 7035-01-060-3835
NSN 6135-00-170-8819
NSN 5975-01-429-6890
NSN 6145-00-435-4013
NSN 6240-00-099-8606
NSN 5965-01-530-8875
NSN 5965-01-198-3256
NSN 6105-00-325-1647