Spread in [Fe/H] for FG stars in 55 GCs (open black squares) as a function of the GC present-day mass expressed by the total absolute magnitude, M_V (Harris 2010). Metallicity spreads were derived from PCMs by L22. Filled red circles and black triangles are spectroscopic [Fe/H] spreads σ_[Fe/H] of GCs and dwarf galaxies, respectively, from Willman & Strader (2012). A few interesting objects are labelled in the figure.