A coupling comprising a receiving part (1), a securing part (9) and an insertion part (17) includes blocking elements (6, 13′) whose engagement preventing the securing part (9) from moving from an extended position into a retracted position is released by the axial displacement of latching arms (13) of the securing part (9) under the effect of a retaining ring (22) upon the insertion of said insertion part (17), such that when the insertion part (17) is properly arranged in a receiving space (16) of the receiving part (1), the securing part (9) can be shifted into the retracted position in which said insertion part (17) is secured. What is achieved in this way is relatively simple modification of the assembly force through design measures, high wear resistance, and simple and operationally reliable manipulation of the inventive coupling with regard to the release of the connection between the receiving part and the insertion part, especially under confined spatial conditions.