This standard specifies A and C grades, large series of flat washers, whose outer diameter is three times the nominal size (thread specification), and is mainly used for hexagonal bolts, screws and nuts with thread specifications from M3 to M36.
GB/T 96-1985 history
2002GB/T 96.1-2002 Plain washers--Large series--Product grade A
1985GB/T 96-1985 Plain washers--Large series--Product grades A and C