Stealth comes in many very different types, depending on what unit in question uses to conceal its presence: Spy, Trade, Legal, Terror, Commando, Stealth Aircraft, Subs, and Stealth Subs. Each of them can only be perceived by certain units, which may see one or more of these classes (which can be checked in "Spot" category). Stealth units never have <l:6,136>Zone of Control<e>, but they also always ignore enemy Zones of Control.