Mass-radius diagram showing the three planets orbiting TOI- 396 (star symbol) along with the exoplanets whose density is more significant than the 3σ level (circle). All the markers are colour-coded according to the equilibrium temperature (T_eq) of the planets. The thick lines are the theoretical MR BICEPS models as detailed in the legend, except for the light-blue line denoted with A21, which is taken from Aguichine et al. (2021). Earth-like means 32.5% iron + 67.5% silicates, while Mercury-like means 70% iron + 30% silicates. Models were computed for T_eq = T_eq,b = 1552 K (dashed-dotted lines), T_eq = T_eq,c = 1309 K (solid lines), and T_eq = T_eq,d = 1061 K (dashed lines). The difference between the A21 model and its BICEPS counterpart is due to different assumptions for e.g. pressure-temperature profiles and opacities. The dotted black lines are the iso-density loci of points corresponding to 0.5, 1, 3, 5, 10 g cm⁻³ (going from top to bottom). We recall that the mass estimate of TOI-396 c (the leftmost star symbol) is not statistically significant and its 3σ upper limit is $M_c^{\text{up}}~4M_{\oplus }$.