I have a mask that supports a 2.5pm filter. This filter will help me in protecting myself for when I am required to wear a mask (such as medical appointments). Considering the filter is only good for 12 hours, it can use up the filters pretty quickly if I should have a significant need for doctor appointments. I do have filters for now, but will obviously order more when I drop down to 2 filters. You can find the filters on Amazon for $10.