Zemax Black Box is an encrypted file that contains lens prescription data. It comes handy when vendor wants to share design with customers so they can ray trace and verify results, yet still keep the design information encrypted to protect vendor’s intellectual property.  

Sometimes the needs arise that user may want to use the ZBB part in mirror space, meaning placing it after a fold mirror. When doing that they find out the ZBB part no longer works. This is one of the restrictions on ZBB file that you may not use the same Black Box ZBB file in both mirror space and normal space. The Black box ZBB file can only be used in the same space the original ZBB file was created in. For example, if the ZBB file is created after 1 fold mirror, then you can only use this ZBB file in the same setup with 1 fold mirror in front of it. You can find it described in the help file at The File Tab > Export Group > Zemax Black Box