100 X PM2.5 Activated Carbon Filters 5 Layers Replaceable Filters For Face Coverings Cotton Cover Mask Inserts

Five Layer Filtration Carbon Filters for Face Masks Sized Approximately 8 x 12 cm Important note: PM2.5 mask filter cartridges should not be washed. In environments with light to moderate pollution, they should be replaced every 7 days, and in heavily polluted environments, every 3 days.