[Zope] Zclass nonfolderish?

After reading Amos' ZClasses Tutorial, my understanding is that you are required to subclass the "Object Manager" base class to create class instances that are folderish. However, even if I leave the base class blank when creating a ZClass, instances of the class present themselves as folderish (e.g. if I visit /myClass/manage, I am presented with a management interface that allows me to add objects "into" myClass). Is this proper? How do I create a ZClass which is not folderish?