These are QTY 20 PM 2.5 Mask Inserts for cloth face masks. 

Add extra protection to your cloth face mask with these PM 2.5 filters. 

• Filters are single-use and disposable. 
• Can be changed daily or weekly depending on usage
• Suits Children/Smaller mouth cover with filter slot
• Can be used with face masks
• Approx. 10 CM x 6.5 CM
• Made of 5 layers with activated carbon and non-woven melt-blown filter cloth
• Good for dust, allergies, pollution, ash, pollen and can be added to cloth masks with pocket