Comparison of the optical depth τ₀ of the strongest X-ray absorption lines at wavelengths below 40 Å (energies above 0.3 keV), from Cloudy, SPEX, and XSTAR calculations for a PIE plasma, ionised by the AGN1 SED, with N_H = 1 × 10²² cm^-2 and σ_v = 200 km s^-1. The displayed data give the ratio of τ₀ from each code relative to the mean τ₀ found by the codes. The τ₀ ratio is shown in blue circles for Cloudy, red diamonds for SPEX, and green squares for XSTAR. The listed lines correspond to the 50 lines with the highest τ₀ values at log ξ of 1.0 (left panel), 2.0 (middle panel), and 3.0 (right panel). The dotted vertical line at τ₀ ratio of 1 indicates where the results from the codes would be identical.