Uncertainty of the mass enclosed within different radii of the galaxies in the training set and in the validation set of the model trained on NIHAO and AURIGA galaxies together. The blue (orange) line shows the median uncertainty for the training (validation) set, while the shadowed region indicates the 1σ interval. The median uncertainty of NIHAO and AURIGA galaxies in the validation set is individually shown as a dashed and dot-dashed grey line, respectively. The dotted pink line and shadowed region correspond to the FIRE testing set.