Test for the size reduction in planetary gaps. The dashed lines correspond to the maximum grain size of the respective model (see color bars for the model parameters), while the solid lines show the dust column density for each model. Thick black lines correspond to the respective DustPy simulation that we want to reproduce. The particle size is reduced on the dust depletion timescale when the large dust population makes up less than the critical fraction ƒ_crit of the total dust density. We run these simulations to determine which value leads to the best agreement with the DustPy simulation.