Radio-power distribution of radio halos at 1.5 GHz versus cluster X-ray luminosity (0.1–2.4 keV). Blue squares represent radio halos in our sample with a size in excess of 0.4 Mpc, red circles mark radio halos with a size below 0.4 Mpc. The line is the best fit to data for a collection of radio halos in Feretti et al. (2012), all in clusters at z <  0.3. The halo with the highest radio power is hosted by MACS J0717+3745.