Bigger cap for 18mm/22mm HEPA filters

thingiverse

bigger cap for 22mm and for 18mm HEPA filters ...(e.g. this one is 18mm: Electrolux EFS1W) original mask needed from https://www.thingiverse.com/thing:4225667 you can check the efficiency of hepa filters and submicron particles here (short: it's very efficient): https://ntrs.nasa.gov/search.jsp?R=20170005166 P.S. I removed the combined internal grid (rejilla) originally missing in the original thing, as it's already there from the author ...