diameter is .3125 grade 8 lock washer, standard.
A washer which is usually round with a centrally located hole. Its edges and two bearing surfaces are so designed that applied pressure brings into play the spring tension and/or frictional locking principle which materially resists any tendency toward turning. It may be made of one or two pieces
NSN 6320-01-240-4637
NSN 5910-01-432-1246
NSN 5930-01-188-6454
NSN 5920-01-268-9512
NSN 2925-00-203-8735
NSN 6240-01-514-7114
NSN 5905-00-238-6406
NSN 6135-01-384-4395
NSN 6320-01-512-2031
NSN 5920-00-866-2477
NSN 5996-01-208-6053
NSN 6610-01-237-5815