Top panel: radio luminosity as a function of rotation velocity for the UCDs observed in the radio domain (mainly at 4.9 and 8.5 GHz). Red solid circles are for M dwarfs, the blue solid circles represent L dwarfs. The solid circles connected by black lines denote different measurements for the same target. Red open triangles denote the upper-limit of the luminosity of M dwarfs; blue open triangles stand for the upper-limit of the luminosity of L dwarfs. The data are mainly taken from Table 1, McLean et al. (2012), and references therein. Bottom panel: the number distribution of the observed dwarfs as a function of rotation velocity. The red solid line is for M dwarfs (normalized by the total number 91), the blue dashed line is for L dwarfs (normalized by the total number 48).