This standard specifies the type 2 non-metallic insert hexagon lock nuts with thread specifications M5~M36, performance grades 9 and 12, and product grades A and B. Group A is used for D<=16 mm; Grade B is used for nuts with D>16 mm. Note: This kind of nut is equivalent to GB/T 6175 plus effective short part. If other technical requirements are required, they should be selected from current standards (such as GB/T 196, GB/T 3098.9 and GB/T 3103.1).