in the cavity formed in the socket the rear end of the socket member is provided with a projection 31 aligned with the cylindrical axis of the socket and which is formed to extend through the aperture 19 disposed in the rear wall 25 of the receptacle whereby it projects beyond said rear wall when the ball end 21 of the extension bar 11 is forced into the socket 27 to be seated therein the expandable sides of the socket first expand to allow the passage of the ball into the socket member and then contract around the ball when it is seated in the socket thereby capturing the ball internally in the socket but with a swivel connection which permits the socket member to partially rotate freely around the ball the socket acts as a bearing member for the ball the socket member 27 with the captured ball 21 is then inserted into the receptacle on the periphery of the mirror holder 13 the external configuration of the socket is formed to mate and fit snugly within the receptacle which has a mating female configuration the slightly tapered cylindrical external surface of the socket member with the larger diameter disposed at the open end is squeezed when the socket is fitted into the receptacle on the holder to securely retain the ball on the extension bar.