GRAVITY K-band spectra at medium spectral resolution (R ~ 500) of the 22 substellar companions with a well-constrained spectral type, sorted from M-type (top) to T-type (bottom). The spectra are scaled with respect to each other by the ratio of the square root of their S/N to their mean flux, and they are offset along the y-axis so that their mean value is located at the height of their corresponding tick mark for better readability. The best fitting spectral type templates from the SpeX Prism Libraries are shown in gray with their corresponding K1 -K2 extinction E_K in units of magnitudes shown on the left. The S/N of each spectrum is shown on the right.