Same ass Fig. B.1, now for Δv_⋆ against metallicity [M/H]. The discs and nuclei of the four galaxies span a very small range which complicates the observation of the possible trends. Regarding the rings, only NGC 1097 and NGC 5248 span a wide range of values of the metallicity. However, they do not present a clear trend and in most of the bins the mean value of Δv_⋆ is not bigger than the typical error.