A coupling assembly having an annular coupling with internal threads in threaded engagement with external threads on opposed tubes inserted into the coupling. An annular gasket of rigid material is mounted between and in engagement with opposed ends of the tubes within the coupling. This gasket has a continuous radial portion extending between these opposed ends of the tubes and a pair of opposed flanges extending from opposite sides of the continuous radial portion and into contact with an interior marginal portion of the opposed tubing ends. Sealing is provided between the opposed ends of the tubes.