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 6220-00-051-4198
NSN 5905-01-373-9885
NSN 6220-01-534-6695
NSN 5950-01-355-8861
NSN 7035-00-800-0770
NSN 5915-01-313-0560
NSN 5895-01-626-1893
NSN 5999-00-058-5475
NSN 6610-01-011-0296
NSN 5996-01-311-1167
NSN 6220-01-527-4276
NSN 6135-01-633-8502