Grain size a_trans for which the participating codes transition from the stochastic to the equilibrium calculation regime. The panels show the smallest grain size that was considered to be in equilibrium for silicate (left), graphite (middle), and PAH (right) grains, for each of the codes, across all of the input fields defined in Sect. 3 (within each panel, the scaled Mathis ISRF fields to the left, and the diluted black body fields to the right).