This video, 

https://www.youtube.com/watch?v=ya9zTstjOI

 is a video about sorting marbles according to size. 

Masks do this with airborne viruses and particles. Viruses come in different sizes. 

Many masks are worse than worthless against C19, for they deceive the users. 

 I’ve read Many ‘health’ masks, sort out particles down to .3 microns, but the average COVID virus measures .125 microns.