A washer having a centrally located hole with a solid or laminated cross-section and two flat parallel bearing surfaces. The hole must be 75 percent or less than the largest dimension and the bearing surface finish is greater than 32 microinch (0.8 micrometer). The thickness cannot exceed 25 percent of the largest outside dimension. When the largest outside dimension is less than 1/4 inch or 6mm, the thickness must be 0.006 inches (0.15mm) or greater and for items 1/4 inch (6mm) or larger, the thickness must be 0.016 inches (0.4mm) or greater. The maximum tolerance is applied to dimensions and used as a determining factor. Items with separable lamination use shim. For items fabricated from ceramic or electrically rated materials by specification or industry standards use insulator (1), washer. Excludes disk, valve, graphite impregnated and lubricated items.
Dept. of the Navy 
Canada Classification: Gaskets, washers and other seals, of vulcanized rubber other than hard rubber
NSN 5950-01-063-7181
NSN 6685-01-527-5561
NSN 5930-01-003-8775
NSN 5950-00-905-4075
NSN 5950-01-596-5112
NSN 5905-01-056-5349
NSN 5855-01-250-2421
NSN 6110-01-367-0977
NSN 5945-01-160-2355
NSN 5855-01-085-5354
NSN 5999-01-362-4033
NSN 6105-01-602-4077