A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6130-01-540-3542
NSN 6620-00-849-0450
NSN 5960-00-477-5895
NSN 6610-00-083-6243
NSN 6135-01-447-5083
NSN 6645-00-376-4829
NSN 5975-01-556-6572
NSN 5999-00-816-7625
NSN 6620-00-193-9503
NSN 5999-01-388-5927
NSN 5965-01-589-3968
NSN 5905-01-212-2751