Relations between the kinematic sizes of nuclear discs and selected bar properties. Top left panel: r_k is correlated with bar size (semi-major axis). The solid line is a simple linear regression fit to the data, whereas the dotted line corresponds to r_k = 0.1 R_bar, the relation suggested in Shlosman et al. (1989). Top middle and right panels: we present how the kinematic size of nuclear discs relates to bar ellipticity and bar-to-total luminosity ratio, respectively. Bottom panels: relations between r_k and different measures of bar strength (from Díaz-García et al. 2016, see text for details). Bar radii and ellipticities are from Kim et al. (2014) and are deprojected. The Pearson correlation coefficient R is indicated in each panel. In Appendix B we present an analysis of the statistical properties of these relations.