Check the listing for details. 10 Pack - PM2.5 Activated Carbon Protective Filter for Face Masks. Condition: Brand New. Listed at 6.35 USD. - Each pack comes with 10 filters - that is, $1 for each filter. Multiple packs can be purchased.- PM2.5 Activated Carbon Protection Filter isolates dust, pollution, smoke and chemicals while providing ventilation.- Five layers: 1st layer: Anti-stick cloth; 2nd layer: Filter cloth; 3rd layer: Activated carbon; 4th layer: High efficiency filter cloth; 5th layer: Anti-stick cloth.- Easy to insert in adult and child face masks with a pocket. Face mask not included.- Recommend using the filter for up to 4 hours and washing the filter after each use.- Each filter can be hand washed in hot water up to 10 times.- Comes with certificate of authenticity.- Size: 12.5cm x 8cm.- Quantity: each pack comes with 10 filters. - Dispatched from Sydney, Australia within 1-2 business days.- Delivered with AustraliaPost - tracking number provided.