Worth it! Recommended if you wear glasses
I've used this with cloth and paper surgical masks. It is a great way to improve the efficiency of most masks. It does not eliminate glasses fogging up, but it substantially cut down on it for me.  I am a registered nurse and I use this for myself and would have my friends and family use them too.  This is an unsolicited review, I did not receive compensation in any way.
Rating: 5 stars