Known T-dwarf binaries. We have represented the spectral types of the secondaries versus the primaries for known T-dwarf binaries (circles). 0 stands for T0, 10 for T10, and 11 for Y0. The color code is related with the projected separation (in au) of the binaries. Most of them show separations smaller than 5 au, while only four show ρ ≥ 8 au. WISE 0612-3036 (filled square) is among these four binaries with a projected separation of 11 au.