Moon mass vs. moon semi-major axis for our sample of large moons around giant planets (two upper panels) and ice giants (two lower panels). The x-axis of each panel is normalised with respect to the radius of each host planet. The radius of the filled circles represents the moon size, and the shaded area around them shows the size of the ring system (as defined in Sec. 3). The moon and ring sizes are scaled using Titan as a standard size. The colour bar represents the lunar density.