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 5895-01-505-9125
NSN 5920-01-651-5136
NSN 6685-01-474-6183
NSN 6220-01-241-4625
NSN 5910-01-144-3106
NSN 5925-01-394-1073
NSN 6620-01-603-6442
NSN 6145-00-076-9324
NSN 5999-01-200-8113
NSN 7035-00-215-3272
NSN 5996-01-245-8209
NSN 6610-00-730-5883