Flexible wheel shape: it is divided into two types: cup shape and hollow shape. The cup shaped flexible wheel is represented by the capital letter C, and the hollow shaped flexible wheel is represented by the capital letter H

Flexible wheel length: it is divided into two types: standard and dwarf. Standard flexible wheel is represented by the capital letter S, while short flexible wheel is represented by the capital letter D

Torque: it is divided into standard and high torque, high torque is represented by G, otherwise it is the standard type

Specification codes (6): they are divided into 14, 17, 20, 25, 32 and 40, corresponding to harmonic gear pitch diameter 35.6, 43.2, 50.8, 63.5, 81.3, and 101.6, respectively