a coupling formed of a tubular body defining an internal channel . the body is formed of a first part for connecting the channel to a circuit element and a second part defining a housing for a pipe end , the first and second parts including mutually engaged end portions , wherein the housing extends into the end portion of the second part and the end portions include facing openings for receiving a clip element for securing the parts to each other . the opening of the second part opens into the housing and the clip element has a locking portion that is elastically deformable from a retaining state to a free state for extracting the clip element . the clip element projects into the housing such that the pipe end prevents the locking portion from deforming to its free state and being extracted .