Comparison between the opacity models that we used at 850 µm as a function of the maximum particle size and for a power-law size distribution with an exponent of q = 2.5. Shown is the opacity cliff (see text for details) at a wavelength of 850 µm (blue and orange shaded regions). The blue line refers to the opacity model from Ricci et al. (2010) with compact grains (labeled R10-0) and the orange line to that of Birnstiel et al. (2018) with compact grains (labeled DSHARP). The green, purple, and red lines refer to 10%, 50%, and 90% porous grains in the DSHARP model. The R10-0 and DSHARP opacity values differ by a factor of ~8.5 at the position of the opacity cliff. As the porosity of the DSHARP model increases, the opacity cliff starts to flatten out, until it completely disappears for very porous grains (90%). The location of the cliff shifts to larger particle sizes as it diminishes in porosity. The black dashed line shows the particle size at 1 mm. The value for the R10-0 model at this size corresponds to , while for the DSHARP to .