Radii and masses of exoplanets with r_P < 4 R_⊕ discussed in the text (gray points). The position of TOI-5076b in this diagram is shown by the black dot. We also represent the position ofNeptune (blue dot). The colored and continuous lines denote mass-radius models for planets with the same composition. In particular: pure iron (100% Fe, brown curve); Earth-like rocky (32.5% Fe+67.5% MgSiO₃, magenta); pure rock (100% MgSiO₃, black curve); pure water (100% H₂O, blue curve);0.1%H2envelope(49.95%Earth-likerockycore+49.95%H₂O layer + 0.1% H₂ envelope by mass), assuming 1 milli-bar surface pressure level and isothermal atmosphere at 700K (red curve).