A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 7035-01-139-5707
NSN 6220-01-032-7370
NSN 6135-01-184-0727
NSN 6145-00-594-7822
NSN 6150-01-483-0525
NSN 6150-01-602-9767
NSN 5985-01-020-8259
NSN 5925-01-540-7580
NSN 6105-00-525-1586
NSN 6105-01-566-6462
NSN 6135-00-444-1402
NSN 5925-01-330-3976