Median TNG100 kinematic transition radii (red, green, and blue solid curves) as a function of galaxy stellar mass, compared with the median transition radius R_T, exsitu between in-situ- and ex-situ-dominated regions (black line). All the curves are obtained from FR galaxies of class 2 (see Fig. 3) with well-defined R_exsitu between in-situ-dominated centers and ex-situ-dominated outskirts. The number of galaxies used to produce each curve is reported in the legend.