Trends in the 1.4 μm feature amplitude of gaseous exoplanets. The featureless spectrum of HD 86226 c (green marker) does not follow the trends seen for other planets. The purple parabolic trend was found by Brande et al. (2024) and describes Neptune to sub-Neptune-sized objects (black markers). Non-filled black markers show GJ 1214 b and the super-puffs Kepler-51 b and d, that were excluded from this trend. Gray markers show the feature amplitudes of gaseous planets calculated by Edwards et al. (2023). Here we only include their results for planets with equilibrium temperatures above 900 K, which mostly correspond to gas giants. The red region shows the feature size predictions of Gao et al. (2020) for planets with gravities of 10 m s⁻² at pressures of 1 bar. This shaded region includes atmospheres with metallicities between 1× (dotted edge) and 10× (dashed edge) solar.