This part of ISO 5692 specifies the requirements for vehicle coupling rings with a ring inside diameter of 40 mm for coupling with the drawbar coupling specified in ISO 6489-2, and for ensuring vehicle coupling with the necessary horizontal and vertical rotation angle. This part of ISO 5692 is applicable to couplings where the vertical static load is not more than 2 000 kg and the dynamic horizontal load is not more than the D value of 120 kN. NOTE For D value , see ISO 6489-2.