I got a 5 pack and they fit really snug and did the blowing out a candle test and the flame did not flicker while I was blowing so they seem pretty solid. The metal nose peice on 1 came off partially but other than that no complaints. Would buy again.
They appear to be of good quality and are not too restrictive to breath through. On the package it does specifically say "non-medical device" which I am fine with, I am not in medicine, just wanted something a little more protective then a cotton mask. I was happy to be able to purchase these through a reputable seller such an Monoprice. Lots of companies I have never heard of selling similar products.