Gas radii versus dust radii of the Herbig disks with detected ¹²CO emission, both R_90%. An upper limit on the gas radius or dust radius, or both, is marked with a triangle pointing in the corresponding direction(s). The colors indicate the Meeus et al. (2001) group of the disk: red is group I, blue group II. Lines for different R_dust to R_gas ratios are shown as well. The black line shows for the resolved disks the relation of the R_90% radii. Using R_68% does not alter the relation significantly. The yellow region indicates the region where the difference between the dust and gas radii cannot solely be explained by optical depth effects, and radial drift is necessary (Trapman et al. 2019). The red line corresponds to the relation found for the disks in Lupus (Ansdell et al. 2018).