Review (4/5): I’d buy them again
These are MOSTLY what I hoped for. They allow breathing to be more comfortable, and, to some extent if you wear them far enough down on the nose, help with the glasses fogging problem. They are plastic to tend to sweat after you’ve worn them and breathed hot air on them for awhile, but they do keep your mask from sucking into your mouth. I’m a singer, so this is important.