The rotational permeability µrot has been calculated as a function of grain size d for a model representing a fine-grained crystalline material in which the easy direction of the magnetization varies from grain to grain. If d increases from zero to the domain wall thickness δ, µrot decreases to ≈ 20 % of µrot at d = 0. If magnetostatic effects are also taken into account, the decrease of µrot shifts to higher d.