Ratio between the mass predicted by the CNN+MAF models, trained on different simulation suites (NIHAO-only, AURIGA-only, or a combination of the two), and the true mass enclosed within various radii of the galaxies in the NIHAO (left panel) and AURIGA (right panel) validation datasets. The blue line shows the median ratio determined using the mass estimated by the CNN+MAF trained on NIHAO galaxies, while the shadowed region indicates the 1σ. The orange line and shadowed region correspond to predictions of the CNN+MAF trained on AURIGA galaxies, and the pink line and shadowed region depict the results of the model trained on NIHAO and AURIGA galaxy projections together. The predicted versus true mass ratios resulting from applying literature mass estimators to either NIHAO (left panel) or AURIGA (right panel) galaxies are shown as grey symbols with 1σ error bars.