Mass–radius diagram for all known planets with masses between 0.5 and 30 M_⊕ and radius 1–4 R_⊕ determined with a precision better than 30%, comprising from Earth-like to sub-Neptunian regimes. K2-292 b is shown in black, while K2-66 b (Sinukoff et al. 2017) is shown in gray. Data are taken from the TEPCat database of well-characterized planets (Southworth 2011). Theoretical models for the planet’s internal composition are taken from Zeng et al. (2016).