J vs. J–Ks colour-magnitude diagram. USco1621 A and B are marked with light blue circles, and USco1556 A and B are marked with red triangles. The photometry of both primaries is obtained from 2MASS and the photometry of the secondaries is taken from VHS. Known members of USco are shown as grey diamonds; the photometry of objects with J < 14 mag is obtained from the 2MASS catalogue, while the photometry for the fainter ones is determined from VHS data. The VHS photometry has been transformed to the 2MASS photometric system through the colour equations provided by CASU. The photometric sequence of field dwarfs derived by Pecaut & Mamajek (2013, squares) Dupuy & Liu (2012, triangles) and Lodieu et al. (2014, diamonds), displaced to the mean distance of USco, is also shown in blue.