Cross-sections of the boundary surfaces of model rotationally supported tori in cylindrical coordinates with z = rcosθ (the equatorial plane of the tori is z = 0). The top panel shows the tori around Kerr black holes with spin parameters a = 0, 0.5 and 0.988. The angular velocity profile index of the tori n = 0.21, and the Kelperian radius r_k = 12 r_g. The bottom panel shows the tori with angular velocity indices n = 0.14, 0.17 and 0.232. The Keplerian radius of the tori is r_k = 8, and the black-hole spin parameter a = 0.998.