Cut from waste fabric. These reusable Linen / Viscose blend fabric face masks have adjustable elastic ear loops for comfort and are supplied with 2x PM2.5 disposable respiratory filters that insert to a bamboo jersey pocket on the inside.
Replacement filter inserts can be bought from various online retailers. Be sure to search for "pm2.5 disposable filters"
Alternatively several studies suggest making reusable ones from a high count, tightly woven cotton fabric folded a couple of times to be equally effective. Do not use loose knit or jersey.