(Half-light) radius at various pass-bands, probing the structure of the torus, as a function of bolometric luminosity. The blue and red circles are our own size estimates from MIDI observations of type 1 and type 2 sources respectively. The green stars are the near-infrared interferometry observations and derived ring-fit radii (Swain et al. 2003; Kishimoto et al. 2011a; Weigelt et al. 2012). The yellow plus symbols are the UV/optical-near-infrared reverberation mapping radii from Suganuma et al. (2006) and references therein; the yellow line is a fit to these data. The scatter in the mid-infrared sizes is significantly larger than in the near-infrared. The error bar for NGC 4151 is not a statistical error but denotes the range for r_1/2 from the upper limit (from single-dish observation) and lower limit from our modeling. The statistical errors of the MIDI size measurements are smaller than the symbols and therefore not shown.