Mass-radius diagram for well-characterised M-dwarf exoplanets with R_p < 4R_⊕. The orange diamond marks the position of TOI-771 b. Previous THIRSTEE M-dwarf planets (TOI-406 b and c, Lacedelli et al. 2024) are labelled and highlighted with solid black contours. Planets are colour-coded according to their equilibrium temperature. The planetary properties come from the PlanetS catalogue (Parc et al. 2024), updated with the more recently published planets from the NASA Exoplanet Archive as of December 12, 2024, having mass and radius precision better than 25% and 8%, respectively. Different theoretical compositional tracks are show: Zeng et al. (2019) models for Earth-like composition (solid green line), and for Earth-like rocky cores with H/He atmospheres by different percentages in mass at 300 K (dotted dark blue lines); Rogers et al. (2023) mass-radius distribution from photoevaporation models (dotted orange line); Turbet et al. (2020) models for water steam atmospheres (dotted purple lines); Aguichine et al. (2021) models for irradiated ocean worlds at 500 K with different water percentages (dash-dotted blue lines); and Luo et al. (2024) models for rocky interior with water dissolution in both mantle and core with different water percentages (dotted grey lines).