A coupling for support members includes a sleeve-like coupling sleeve having screw-in openings that proceed from two opposite sides and are each provided with an internal thread. A radially inwardly directed mounting protrusion is formed between the two internal threads in the screw-in openings on the inner side of the coupling sleeve. A radial recess is formed in each case between the mounting protrusion and the internal threads, the recess adjoining a runout of the adjacent internal thread. An elastically deformable sealing ring is inserted in each case into the two recesses. In the unloaded state of the sealing rings, the outside diameter thereof is greater than the inside diameter of the mounting protrusion and/or greater than the core diameter of the internal thread. The coupling has a clamping ring, the outside diameter of which is smaller than or the same as the inside diameter of the mounting protrusion.