Mass-weighted [Z/H] gradients measured along bar major axis (green pentagons), and along its perpendicular direction (black squares), as a function of the bar length (in units kpc and R₂₅), total stellar mass, and offset from the global main sequence of galaxies (ΔMS), for 14 barred galaxies in our sample. The red line is calculated following Eq. (5). It is defined to be positive in galaxies that show a flatter gradient along their bar major axis, compared to the bar perpendicular direction, and negative values otherwise.