They work, they just aren't comfortable
My co-worker saw how my masks sucks in when I breathe (I have asthma and it just seems like I have to breathe harder than most in my mask), and she told me about these devices that look like a sports cups that are supposed to help.  So, I immediately bought some.  First of all, they do work.  I feel like I can breathe better without my mask collapsing on my mouth every breath.  But, they are not comfortable.  They dig into the bridge of my nose.  I do wear glasses, so that may not help.  Also, it really depends on the mask if these help with fogging.  Some style of masks work better avoiding fogging that others.  I'm not sure these are the fix for fogging, rather a different style of mask.  Just my 2 cents.
Rating: 3 stars