Left: infra-red spectral type determination for a candidate member observed with Subaru. The templates used for comparison (red spectra with corresponding spectral type label) were also obtained with Subaru and correspond to known L and T dwarfs from Geballe et al. (2002). A visual comparison with the spectra obtained by Lodieu et al. (2008) of Upper Sco members also suggests that a L spectral type is a closer match especially based on the water bands and the “peaky” structure  ~ 1.7 μm. Right: our own re-calibration of the reddening independent I_H2O index from Comerón et al. (2000). The dotted black line represents the linear relation found by Comerón et al. (2000), while the red line is the best linear fit to our data and is the relation that we have used to estimate the spectral types of our M candidates.