GES vs. Gaia metallicity (uncalibrated, calibrated, and calibrated with open clusters) for 136 stars belonging to 34 open clusters in common. The panels on the left show the member stars individually and the average metallicities per cluster, and the panels on the right show the histograms of the metallicity distributions of both samples and their difference Δ. The size of the symbols is proportional to the number of members. The light-blue bands indicate an agreement between ± 0.2.