Rotational frequency vs. diameter for the sample of asteroids having photometric inversion solutions passing the rejection filter described in Sect. 3.1 (8670 objects). Red symbols are used to indicate asteroid family members according to Milani et al. (2014). They are displayed in red just to emphasise the large contribution of asteroid dynamical families in our inventory of objects having sizes smaller than about 10 km, including many slow-rotators.