Seems to work as described
I have been using this filter for about 4 weeks and it fits into a cloth mask I have with an internal pocket for filters. I do not have problems breathing through the filter. I haven't used it long enough to know how long each filter will last but so far I am pleased and see no reason why I would not buy more if and when they are needed. I should note that I work from home and do not get out much due to COVID so I have not used the filter a great deal.
Rating: 4 stars