Hi ChimeraX-ers, Finding an equivalent contour level for 3D classes in cryoEM can be challenging, particularly if the density histograms are sufficiently different that setting a single level does not suffice (and particularly when comparing many classes from a large classification). The options "enclosevolume" and "fastenclosevolume" for the "volume" command are very useful for this (e.g. "volume #* fastenclosevolume 200000"), but fail in the presence of compositional heterogeneity (if there is more ordered stuff in one class and the volume is fixed, the contours will no longer be equivalent). To address this, would it be possible to add a "within_radius" modifier for the "volume fastenclosevolume" command? This would mean one could then set a fixed volume to be enclosed by the contour within a set radius of either the center of rotation, or of an atom selection, making the contour levels at least locally equivalent (which is often what one wants for the purposes of comparison). Cheers Oli