What's there to say? We sell some amazing reusable face covers, but some people want to add a little more to them. If you want a little more coverage, we've got some great PM2.5 Mask Filters that slide into our 4 Layer Face Covers perfectly. That means 9 layers of interference between you and the world. These come in packs of 10, which should last you long enough to at least get through that copy of War and Peace you insist on reading in public (Ed: That's weirdly specific, maybe we should use a different analogy and you should cool it with the Russian Lit?).
These filters have a meltblown fabric and nonwoven fabric layer on either side of an activated carbon filter, giving you the same materials that are used in disposable masks with so much less waste.
There's no styling to these, just pop them into your mask. We can't say exactly when you should replace your filter, but we generally say replace it weekly or after about 60 hours of continuous use.