Mass of grains as measured from belt flux densities at 1.33 mm as a function of the radius of observed planetesimal belts (all points with error bars). Each panel focuses on a different subgroup of REASONS belts (shown as the white points, rest of the population in grey), those orbiting stars in the Sco-Cen association (left), young moving groups (middle) and field stars (right). In all panels, the background colour map represents the selection probability (%), or percentage of belts in that subgroup that would pass the selection effects at a given [Mass_1.33mm-R] location, assuming unobserved belts have the same distribution of parameters [d,R_BB/R, L_⋆, λ₀, β] as the observed population. The changing colour maps in each panel show how selection biases vary depending on stellar properties and observing strategies employed for different subgroups.