A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6650-01-145-2754
NSN 6150-00-760-4566
NSN 5990-00-067-6791
NSN 6145-00-146-9600
NSN 5915-01-125-5120
NSN 5965-00-529-0602
NSN 6110-01-437-5779
NSN 5998-00-216-7436
NSN 7035-01-471-4884
NSN 5945-00-226-2013
NSN 5960-01-150-3944
NSN 5965-01-055-7645