You can place it in any mask and it works!
I love its ability to keep the mask off of your mouth, so you are not breathing the mask into your mouth as you speak.  It also does not fog up your glasses!  It makes the breath go down and away from your glasses.  I have given them to my family for Christmas stocking presents, and everyone loves them!  If you are a lipstick or lip gloss wearer, you will appreciate that the mask is not touching your lips!  I love these.
Rating: 5 stars