A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 5855-00-014-5008
NSN 5935-01-438-3818
NSN 5965-00-396-3411
NSN 6150-01-392-0592
NSN 5935-01-272-7205
NSN 5855-00-491-7079
NSN 5835-01-030-8914
NSN 7035-00-411-8850
NSN 6685-01-545-7098
NSN 5985-00-519-5909
NSN 5915-01-542-3452
NSN 7035-00-171-0804