Brightness temperature as a function of radius calculated from the 1.3mm continuum images of Sz 65 (red) and Sz 66 (blue) compared with the results of the DSHARP survey (grey). In addition, we plot the radial profile of the well-resolved compact disc CX Tau (Facchini et al. 2017). All DSHARP discs are plotted in the top panel. Only discs classified as compact are plotted in the lower panel and are listed on the right side. Discs with a derived disc size >50 au are plotted with dashed lines.