There are two width systems for V-belts and pulleys, namely the reference width system and the effective width system. The reference width system defines the groove shape and size of the pulley based on the position of the reference line and the reference width. When the pitch surface of the V-belt coincides with the reference diameter of the pulley, the reference width of the pulley is the width of the corresponding position in the groove of the V-belt pitch surface, used to represent the cross-sectional characteristic value of the pulley. It is not affected by tolerances and is the basic dimension for wheel and belt standardization.