Product review (3 stars): Not for use with an ultrasonic humidifier.
When it arrived, I found out it is not to be used for an ultrasonic humidifier.  This may have been my fault or the information was not clear. I ended up giving it to a friend who does not have an ultrasonic humidifier. I gave it 3 stars because I have not used it. I will update, once I speak with my friend to assess how it works, so refer to other reviews.