Hi all, This might have an easy answer, apologies if I have missed something on the list. I am using a GeomVectorField to store my agents. I need to be able to get back to the original Agent object, not just its associated MasonGeometry. I create agents and add them to the GeomVectorField a bit like this: Agent a = new Agent(); agentGeomVectorField.addGeometry(a.getGeometry()); schedule.scheduleRepeating(a); That basically works fine, but now I want to be able to get back to the underlying agent. I guess I could maintain a separate List of agents as well as the GeomVectorField, or I could add the agent to its MasonGeometry's userData field. Any opinions on which would be best? How else have people stored their agents and their geometries using geomason? Thanks in advance, Nick