pulled away from the connecting sleeve 16 to separate the coupling device b from the connecting device 8 similarly during assembly the casing 4 can be pushed on to the sleeve 16 to attach the coupling device b to the connecting device 8 the cylindrical inner wall of the connecting sleeve 16 is formed with an axially extending groove like portion 25 of reduced thickness as shown best in fig3 the flange 11 of the larger plug pin 7 engages within this reduced thickness wall portion 25 in this way the larger plug pin 7 can be accommodated on the common pitch circle together with the plug pins 6 without needing to increase the diameter of either the retaining disc 5 or the connecting sleeve 16 consequently there is no need to increase the diameter of the casing 4 the rear face of the axial extension 18 defines an annular shoulder 32 for supporting the protective sheath 3 which is firmly clamped between the clamping sleeve 15 and the backing sleeve 17 the wall thickness of the axial extension 18 and of the overlapping end of the connecting sleeve 16 is greater than in their remaining zones so that no weakening is caused by providing the recesses 19 and 20 in these zones fig5 shows the second form of connecting device 8 39 which interconnects a multi line hose a 39 and a coupling device b 39 the connecting device 8 39 is generally similar to the connecting device 8 of fig1 to 4.