This ball, in addition to the 3 rings, has a heavy sphere at its center, from which 6 spokes emerge: two polar spokes and four equatorial spokes. These spokes are strongly attached to the 3 rings at their 6 (six) intersection points, as shown in the graphic. The central sphere can be hollow and provided with a plug so that, by means of a filling, the weight of the COR can be regulated.
You can also fill the hose with chain or weights, to give more weight to the Cor, dispensing with the central sphere.