You will need 2 caps and 2 tamping plates for every small, medium, or large mask. The caps and inserts fit all 3 sizes. You will also need 2 sturdy straps, a piece of 14 gauge copper wire (or a thin piece of aluminum, or a couple of unbent paperclips, e.g.) for the nose, and filter material. As of now, we have had good qualitative test results with one layer of Halyard wrap, or one layer MERV 13 filter with a cotton round as a pre-filter. Weld the chin and nose seams together with a soldering iron, or wood burner, set to a low temp, to create an air-tight seal.