How realistic are models of disordered materials? Comparing and assessing the quality of atomistic configurations is a non-trivial in the absence of long-range periodicity. Cliffe and Goodwin (pp. 949–956) suggest two metrics for this task: namely, local geometric invariance and the degree of local symmetry. The cover image shows a configuration of a-Si where the atoms have been coloured according to the second of these criteria, with atoms in low symmetry environments shown in red and those in high symmetry environments in blue. These new metrics enable screening for structural simplicity in a way that does not rely on formal group theoretical language and outperforms established measures based on simple pairwise correlations.