Transmission spectroscopy metric (top), and planetary radius (bottom) as a function of the equilibrium temperature for small (<4 R_⊕) well-characterized planets from the PlanetS catalog (Otegi et al. 2020; Parc et al. 2024). The population is divided following Kempton et al. (2018): terrestrial planets (<1.5 R_⊕) in light green, small sub-Neptunes (1.5-2.75 R_⊕) in light blue, and large sub-Neptunes (2.75−4 R_⊕) in dark blue. TOI-4336 A b, TOI-4336 A c, TOI-4342 b, and TOI-4342 c are highlighted as pink, blue, orange, and green stars, respectively.