This is a refill pack of filters that are used with the cotton mask and not a mask in itself. These are to be used in Washable Masks. How to use: There would be one packet of four filters. Pick out one filter from the packet and insert it in the pocket of cotton mask. Each filter has life of upto 100 hours under standard conditions. When the filter gets dirty after use due to pollution, you need to replace the filter with a new one. This pack is accessory to PureMe washable mask to ensure that you can change the filters and keep using the mask.