The effective width system stipulates that the outermost width of the edges on both sides of the wheel groove is the effective width. This dimension is not affected by tolerances, and the diameter at the effective width of the wheel groove is the effective diameter. Due to differences in size systems, the length of the tape is represented by the reference length and the effective length, respectively. The reference length is the circumference of the V-belt located at the reference diameter of the measuring pulley under the specified tension force; The effective length is the circumference located at the point where the effective diameter of the measuring pulley is measured under the specified tension.