This filter is for spare part of Aero Breath electronic mask. A new concept mask product consisting of a fan, a battery, and a filter can be used for Semi-permanently except filter. and the one filter is available to use 100 days, you only change the filter 4 times in a year. We definitely recommend this product for people who works in a dusty place, painting, woodworking etc something lots of dust. Micro dust could trigger respiratory diseases or cancer. with Aero Breath Mask, let's prevent it.