Comparison of candidates associated with the MCXC catalogue and the expected L_X,500−M₅₀₀ scaling relation (red line). The parallel dashed lines identify the region of the plane within 2σ_int from the expected scaling relation, where σ_int is the logarithmic intrinsic scatter of the relation we used. Black points are confirmed MCXC associations, while magenta squares mark the associations discarded by the L−M criterion. Pairs of coloured diamonds mark the two possible counterparts for objects with multiple associations.