Hi Stephen, I'm looking into making the Clump class a subclass AMR3DData. I'm working on a test to see if doing this is as fast and memory conservative as your solution here. When running the clump finder, I'm running into issues inside the isBound function when it tries to access another quantity called MatterMass. MatterMass doesn't seem to be returning a single quantity, but something closer to a mass field. Do you know why this is a derived quantity and not a derived field? If not, I think I'll just change it.