Inferred masses for the 893 NORAS/REFLEX clusters as a function of redshift. The cluster sample is flux limited. The right vertical axis gives the corresponding X-ray luminosities scaled by E(z)^−7/3. The dashed blue lines delineate the mass range over which the L₅₀₀−M₅₀₀ relation from Pratt et al. (2009) was derived.