5310-00-187-4128 (FFW92TYPEAGRADE1CLASSB)
NSN 5310-00-187-4128 (NIIN 00-187-4128) is a flat washer in Federal Supply Class 5310, Nuts And Washers — a washer having a centrally located hole with a solid or laminated cross-section and two flat parallel bearing surfaces. Manufacturer part number FFW92TYPEAGRADE1CLASSB (Federal Specifications Promulgated, CAGE 81348); also referenced as FFW92TYPEAGRADE2CLASSB (Federal Specifications Promulgated).
Key specs: 94 rockwell b maximum hardness; full characteristics table below. NIIN assigned January 1963; DEMIL A (none required). Related NSN 5310-00-274-7957.