Mass-radius diagram of VLMS (M ≲ 0.2   M_⊙). The symbols represent observed stars, while the lines correspond to theoretical mass-radius relations. Red rectangles are secondary stars of main-sequence EBs, green circles are secondary stars of white dwarf + M-dwarf EBs, and blue diamonds are single stars (all references are given in Table 5). The black triangle stands for C4780 B. Solid blue lines correspond to theoretical isochrones of solar metallicity and ages of 0.25,1, and 5 Gyr (going from top to bottom along the 0.08 M_⊙ line) from Baraffe et al. (1998). To illustrate the effect of metallicity on size dashed-red lines show the Dartmouth isochrones (Dotter et al. 2008) of 1 Gyr for [Fe/H]  = 0.2 (upper line) and [Fe/H]  = −0.5 (lower line).