I have been using the Clapiel BNF AirClean Disposable Black Masks which have melt blown filters and are made in South Korea.
What I like about this is that its similar to a brand that I purchase, when I travel to Japan (which comes with 5 for the same price) but in this case, you get 50 pieces for under $15, which is great.
It fits very well, covering my nose and mouth and for the most part, are well-made for disposable black masks.
The Clapiel BNF AirClean Disposable Black Masks are recommended!
