The idea is a mask frame that uses any kind of filter material such as: paper towels, shop rags, vacuum filters, cloth and others (see https://www.maskfaq.com/test-results) for material info. Small locking clips hold the filter material to the frame with the filter material mainly in contact with your face, not the frame. The frame length is adjustable from 4.25 – 6 inches. Use rubber bands or string to secure the mask to your head. I printed with ASA and PETG. Note: This mask is not as effective as a N95 HEPA, MERV 16, etc. but this is better than nothing.