wherein, the body is provided with a roughly spherical outer hub, and a plurality of holes are also formed on the body, and the plurality of holes are evenly distributed around an outer surface of the body;

wherein a second magnetic part of the plurality of second magnetic parts comprises a closed end and an open end, and a diameter of the closed end is larger than that of the hole;

wherein when the plurality of second magnetic parts are attached to the body, the open end is embedded in the holes, so that the body forms a substantially regular ball;

wherein the open end continuously extends toward the closed end to form a convex column, wherein the convex column has an outer wall surface and an inner wall surface, and the inner wall surface defines a receiving groove; and

wherein the second magnetic part further comprises a magnetic buckle, and the magnetic buckle is arranged in the receiving groove, wherein a side surface of the magnetic buckle is closely attached to the inner wall surface, so that the magnetic buckle is firmly arranged in the receiving groove.