Mirrored domains are special pairs of domains where registration one of them, the second is automatically reserved for the owner of the first and no one else can register it.
Mirror Domain Zones:
Only the owner of the first one can register the second mirror domain and only with the same registrar where he is registered. Transmit one of the domains in our system is prohibited to another owner, you can only transfer together. Transfer mirrored domains to another registrar are also executed simultaneously.