G′′ values inferred from the comparison of SEDs of T dwarfs (generated from SpecXPrism spectra) with the SED of GJ 578 B. The re-normalized SEDs, whose flux in the CH4L passband respect the upper limit set for GJ 758 B, are reported as filled dots. Those which do not are shown as open circles. The G′′ values for the objects considered in Fig. 4 are overlaid. We also report the value for the red T8 dwarf WISEP J231336.41-803701.4, whose SED, along with the one of the red T8 WISEP J161705.75+180714.0, provide the best visual fits to the SED of the companion.