Our 10 Pack Filters include x10 certified PM2.5 Filters. These Filters have 5 important layers including filter cloth and activated carbon layers. Using a PM2.5 filter can help increase the filtering performance of our reusable cloth masks. They are easy to use, just slip one inside the pocket layer of any of our 3 LAYERED MASKS. These Filters are NOT compatible with our 2 Layered Masks. Ensure to replace your filter up to every 7 days depending on amount of use. Please discard of any used filters respectfully. Returns/Exchanges. Due to health and sanitary regulations there is no Exchange or Return on any GOOD MASK products.