A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6240-00-239-0159
NSN 5996-01-009-0428
NSN 5895-01-017-9896
NSN 6610-01-465-1320
NSN 6220-01-017-3395
NSN 5990-01-434-7913
NSN 5950-00-592-3359
NSN 6650-00-238-1199
NSN 6240-01-328-8999
NSN 5975-01-634-0678
NSN 5835-00-447-1924
NSN 6240-01-014-5598