Posterior distributions when the logarithm of the cluster mass is recovered for proj0 of halo-4 at z = 0.22. The black curve shows the reference case, where we model both the mass and the concentration, as in the top panel of Fig. 5. The other histograms show the posteriors when a parametrisation of the concentration-mass relation is assumed; in particular, the orange and olive curves refer to the cases with a constant value of c₂₀₀ = 3 and c₂₀₀ = 4, respectively. The vertical dashed black line marks the true value of M₂₀₀ as computed by AHF.