closed by threading a screw 7 from the countersunk screw hole 131 into the threaded hole 112 whereby the segments 11 13 are tightened together to form a circular collar like member the interconnecting member 2 includes a base 21 and a projected shaft portion 22 the shaft portion 22 has an external diameter close to an internal diameter of the bearing 3 an internally threaded through hole 23 is centered in the base 21 and the shaft portion 22 for the screw 6 to thread through from the threaded hole 111 on the segment 11 of the annular holder 1 so that the annular holder 1 is firmly connected to the interconnecting member 2 external threads 24 are also provided around an outer side wall of the shaft portion 22 the head member 4 is of a size slightly smaller than the palm of a user and has a smooth and generally spherical top surface with a plurality of arcuate recesses disposed along a periphery of the top surface so that the head member 4 is suitable for gripping by a hand a small shallow arcuate recess 43 is centered on the top surface of the head member 4 for a trademark or other mark to attach thereto the head member 4 is formed at a bottom side with a shaft body 41 a bore is formed inside the shaft body 41 to receive the bearing 3 therein the bearing 3 is received in.