Relative error of M₅₀₀ with respect to the separation between the true and the considered centre for the mass reconstruction. Colours indicate the true M₅₀₀ and markers the mass density model. We consider the same separation for the four models, but gNFW, tNFW, and Hernquist markers have been shifted for visualisation purposes. The black dashed line indicates a 50% error in M₅₀₀.