I bought a pack from Boots, and I used one for the first time today on a hospital visit, so it was on for about an hour and a half. It was so uncomfortable and hot. My glasses steamed up so much that I ended up taking them off. My distance vision isn't too bad, so I could just about manage without them. The cheapo ones I got from Amazon were better, but I think I'll have to try some alternative kind of face covering.