Redshift (top panel) and mass distribution (bottom panel) of the selected cluster sample. The solid blue histograms represent the distributions of all WL15 clusters within the redshift and mass ranges where the richness-mass relation was calibrated. The yellow histograms show the distributions of the clusters with mass above 1.5 × 10¹⁴ M_⊙, while the green histograms show the distributions of the clusters with z < 0.5. The dashed purple histograms show the distributions of the clusters that have at least four associated galaxies. Finally, the red histograms represent the distributions of the final selected cluster sample.