Distribution of the redMaPPer clusters detected as XC1, as a function of richness and redshift. In total, 92 matches with C1 X-ray clusters for 270 input redMaPPers are found within a radius of 1′. A posteriori recovered correlations are not included in this plot (see Fig. 14 for a complete census). Colour coding gives the percentage of redMaPPer detected as C1 in each diagram pixel; greyed pixels stand for redshift-richness combinations not present in the input OPT→X catalogue (Fig. 3)