Density-equilibrium temperature diagram of warm-hot exoplanets with a radius of less than 3 R_⊕ around M dwarfs. All planets have mass determination by either RVs or TTVs. TOI-1685 b is labeled and marked with a thicker black borderline. Some densities are marked as reference by horizontal lines, including Earth (dashed orange), H₂O (blue), and 50% H₂O, 50% silicate (green). The observed ρ-T_eq space before the discovery of TOI-1685 b is shaded in red to illustrate the dissimilarity of TOI-1685 b with previous discoveries.