Abstract: An assembly for connecting together fluid-conducting spigot and socket members employs a U-shaped locking clip with parallel legs sliding in chordwise passages of the socket member. The spigot member has an external groove which is engaged by the legs of the locking clip intruding into the socket when the spigot is inserted into the socket and the clip is slid into its operational position. The clip can be retained in this position by the "snap" engagement of the base portion of the U-shape with a transverse groove in the face of the socket member. The assembly is particularly useful for connecting a demand valve into the facemask of a breathing apparatus.