threaded filter mask

This is a solid filter mask with a 48mm threaded stub to be equipped with filter material cut from e. g. vacuum cleaner bag, 44mm in diameter and min. 8mm thick.
In order to safely keep back the corona virus this filter should be of highest quality, either FFP3 material or from vacuum cleaner bags capable of holding back microparticles the size of sneeze droplets carrying corona... which is .03µm in diameter.