Redshift distribution for complete samples of faint X-ray selected clusters from the RIXOS survey. The dotted datum represents a candidate cluster with an assigned redshift of z=1.0. Smooth curves show the predicted redshift distributions for several evolutionary models: (i) a non-evolving cluster population; (ii) a self-similar model with n=-1.95 spectral index; and (iii) the best-fitting preheated intracluster medium model (with spectral index parameter n=-1.5). [TIFF]