Normalized distribution of mass for the groups identified in SDSS-DR12 by Rodriguez & Merchán (2020). The complete sample is shown in panel a; meanwhile, in panels b and c subsamples with 12 < log₁₀(M_group[h⁻¹ M_⊙] < 13 and 13 < log₁₀(M_group[h⁻¹ M_⊙] < 15 are shown, respectively. In all cases, the complete group samples (or subsamples) are in yellow lines, the groups inside voids are in blue, and the groups inside FVSs are in red.