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 4140-01-545-0270
NSN 5855-00-156-5489
NSN 5915-00-320-4343
NSN 6620-01-146-6968
NSN 6610-01-522-5751
NSN 5915-00-909-5432
NSN 4140-00-953-2004
NSN 5945-01-452-8385
NSN 5895-01-041-8912
NSN 6240-01-571-5181
NSN 5835-01-512-4834
NSN 5915-00-823-1559