Mass-radius (left) and insolation-radius (right) diagrams in Earth units. In the two panels, open circles are transiting planets around F-, G-, and K-type stars with mass and radius measurement better than 30% from the TEPCat database of well-characterized planets (Southworth 2011), filled red circles are planets around M dwarfs with mass and radius measurement, filled yellow circles are planets around M dwarfs with mass determinations lower than 30% or without mass constraints at all (right panel only), and the red star is TOI-1235 b, whose radius and mass are determined with accuracies of 5 and 10%, respectively. In the left panel, the color lines are the theoretical R-M models of Zeng et al. (2016), and the three planets with mass determinations lower than 30% are K2–3 b, BD–17 588A b, and LHS 1815 b. In the right panel, we plot the R-S point density of all the known confirmed transiting planets with contours, and mini-Neptunes and super-Earths density maxima with white crosses. The M dwarf without mass determination in the radius gap is K2–104 b (Mann et al. 2017), a planet around an active star in the Praesepe cluster that is fainter by 5 mag in V than TOI-1235.