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 5855-01-406-4821
NSN 5945-00-875-2104
NSN 6320-01-512-2031
NSN 6105-00-527-8571
NSN 5925-01-381-0614
NSN 5965-01-258-5662
NSN 5965-00-226-7870
NSN 5855-01-312-5160
NSN 5910-01-175-0231
NSN 6220-01-331-3468
NSN 5895-01-193-8157
NSN 5855-01-372-1622