Radius-mass diagram of HD 63433 b and c, together with all exoplanets (grey dots) with a precision better than 8% in radius (by transits) and 20% in mass (by RV). Young exoplanets with measured masses are plotted as coloured dots according to their ages. The uncertainties on the HD 63433 b and c planets are shown as coloured shaded regions with 1, 2, and 3σ levels of confidence. The dashed grey lines are constant density lines. Coloured lines indicate different composition models without gas (middle panel) and with a gas envelope (right panel) from Zeng et al. (2019). Earth and Neptune are also depicted as reference. B22 and M22 refer to Barragán et al. (2022) and El Mufti et al. (2023), respectively.