Vertical gradient of rotation in a finite-width disk model with the Mexican hat vertical profile (solid lines), as a function of the altitude above the mid-plane (z = 0), shown at r = 4 kpc for various width-scales h. For comparison, the (dotted line) shows the gradient behavior in the limit of the infinitesimally thin disk model (h → 0). The convergence on that limit is point-wise continuous, although not uniform – the gradient for h = 0 is discontinuous at z = 0. For higher altitudes, the gradient behavior is universal beyond the main concentration of masses.