piece is prepared for assembly by inserting the seal 30 into the receiving recess in the internal surface thereof the joint is then completed by locating the male connecting piece into the female connecting piece and tightening the nut 24 into the threaded end extent of the female connecting piece tightening of the nut 24 is facilitated by the provision of radially projecting circumferentially spaced lugs 40 on the outer surface of the nut to which tangential forces can be applied once the nut is fully tightened the position illustrated in fig1 is achieved the clearances being such as to take up all axial movement between the two connecting pieces whilst at the same time ensuring an effective seal between the two connecting pieces and permitting relative swivelling about the central longitudinal axis of the joint more particularly in the assembled condition of the joint the seal 30 is radially compressed whereby the surfaces 34 36 thereof seal against the opposed radially spaced surfaces on the male and female connecting pieces respectively the configuration of the seal is then as shown in fig2 b bearing surfaces of substantial axial extent are provided between the bearing member or shell 22 and the correspondingly shaped inner surface of the female connecting piece and between the inner surface of the cylindrical bearing member 26 and the outer surface of the male connecting piece thus the area of bearing contact between the two movable components is substantial and whereby the joint can withstand substantial nonaxial forces applied thereto without any distortion of the components thereof further the seal 30 being radially.