Filter pack - breathing mask replacement

Why make your own* 2 1/2" x 2 1/2" replacement filters for our breathing masks. Each filter consist of one piece MERV 12 filter and one piece MERV 16 filter. Package contains 10 pairs. *Make your own by purchasing a MERV 12 and a MERV 16 furnace filter, remove the filter material and trim to size. Some people make their filters from HEPA vacuum bags and even micro-fiber shop towels.