This standard specifies the type, size, technical conditions and marks of hexagon thin nuts with fine pitch. This standard applies to thread nominal diameter D = 8 mm ~ 64 mm, performance grades 04, 05, A2-025, A2-035, A4-025, A4-035, CU2, CU3 and AL4, product grades A and Grade B, fine thread, chamfered hexagonal thin nuts. Grade A is used for nuts with D≤16 mm; Grade B is used for nuts with D>16 mm.