De-projected semi-major axis of rings, normalised to R_25.5 and in physical units, as a function of the bar strength, estimated from the m = 2 bar Fourier amplitude (left and central panels). The disc-relative sizes of rings are also compared to the bar torque parameter (right panel). The colour palette is the same as in Fig. 2, separating inner and outer rings. The Spearman’s correlation coefficient and significance of the correlation for the inner rings is shown above the figures. The dashed black line corresponds to the linear fit to the cloud of points for the inner rings.