A coupling unit for use in the evacuation and pressure filling of medium by coupling to a filling stub (5), e.g. on vehicles or at similar locations with difficult access conditions, said coupling unit comprising gripper means (8) and locking parts for holding the gripper means (8) in an open or a closed posi­tion, said coupling unit (4) comprising a seal (9) for sealing the connection between the coupling (4) and the end of the filling stub (5), and wherein an actuator (6) affects a gasket holder (20) via a biasing unit (18) and a spring means (19) with an axial pressure, and an outer jacket (7) is mechanically connected with the actuator (6) so that when the inner filling parts (10, 14, 15, 18, 20) are moved in an axial direction to a filling position, the outer jacket (7) is moved in the same direction, whereby locking of gripper means (8) in engagement takes place.