Comparison of calculated a) k from Equations (1, 4), b) F from Equations (2, 5) and c) k from Equations (3, 6) to the observed values of permeability and formation factor in the sintered glass beads. The meaning of the different symbols is explained in the inset, where k(z) refers to Bernabé et al. Equation (4), F(z) to Equation (5) and k(F) to Equation (6). The vertical error bars (dark purple) represent minimal estimates of the model tolerances (i.e., δk/k ≈ ±30% and δF/F ≈ ±10% for the PWB model as well as the Bernabé et al. model applied to high porosity samples; δk/k ≈ ±50% and δF/F ≈ ±20% for the Bernabé et al. model in low porosity samples).