The Moment of Inertia for a thin circular hoop is a special case of a torus for `b=0`, as well as of a thick-walled cylindrical tube with open ends, with `r_1=r_2` and `h=0`. The following formula is used to calculate moment of inertia: `I_x=I_y=(mr^2)/2`, where:
The formula and equation for Moment of Inertia are from Wikipedia (https://en.wikipedia.org/wiki/List_of_moments_of_inertia).