Comparison between the low-resolution SEDs (R = 500) of XSL spectra and the nearest GSL spectrum, when adopting the fundamental parameters of Arentsen et al. (2019). Only extinction is allowed to modify the energy distribution of the theoretical spectra. The color-coding shows D (Eq. (1)), as measured in the UVB, VIS, and NIR arms and across the whole spectrum.Open symbols correspond to spectra for which no slit-loss corrections were applied. 1-σ flux calibration errors correspond to D ≃ 0.03 in each of the UVB, VIS, and NIR arms.