Properties of our sample of 12 barred galaxies (coloured symbols; see legend) and comparison with 508 barred galaxies in the S⁴G survey (grey contours; disk inclinations lower than 50°), as reported in Díaz-García et al. (2016b) and Díaz-García et al. (2019a). Upper left panel: gas fraction as a function of the total stellar mass. Error bars indicate the error on M_* associated with a 30% uncertainty on the mass-to-light ratio (Eskew et al. 2012). Lower left panel: bar length (in kiloparsecs) vs total stellar mass. Vertical error bars are associated with the distance uncertainty, which is typically 15% (Muñoz-Mateos et al. 2015). Upper right panel: deprojected bar ellipticity as a function of the revised Hubble stage. Error bars indicate the typical 10% uncertainty due to 2D deprojection effects for inclinations lower than 60° (Zou et al. 2014). Lower right panel: bar normalised m = 2 Fourier amplitude (available for 11 galaxies) vs Hubble type. On the x-axes of the last two panels small random offsets (≲0.3) were added to the T values (integers) to avoid point overlapping.