Planetary radius vs. mass of known exoplanets, with histograms in the right and top panels depicting the distribution of radii and masses, respectively. The sample is from the TepCat database (Southworth 2011) and includes exoplanets with mass and radius constraints better than 50 and 20%, respectively, and equilibrium temperatures of planets (T_eq) between 300 and 2500 K. The light pink highlighted region represents the sub-Saturn classification, while the black dashed line represents the iso-density curve for ρ_P = 2.52. The red, orange, green, and blue solid curves represent the M-R diagram for pure-iron, pure-rock, pure high-pressure ices (Zeng et al. 2021) and pure H₂ core composition (Becker et al. 2014), respectively. The Solar system planets are represented as black dots. TOI-6651b is positioned above the pure ice composition, indicating the presence of a significant fraction of a H/He envelope.