Observed J magnitude vs size of candidate galaxies at z ~ 7 for all the six fields analysed. The black circles indicates galaxies in the UDS field, while crosses are associated to objects in the EGS field. The solid lines show the 50% completeness levels of the six different surveys for an input simulated profile of exponential disk galaxy. The galaxy size (Rh_out) is the observed half light radius in arcsec measured by SExtractor and it is not deconvolved by the PSF.