"A team of researchers . . . from the University of Cambridge, carried out a series of different fit tests, and found that when a high-performance mask — such as an N95, KN95 or FFP2 mask — is not properly fitted, it performs no better than a cloth mask . . . We know that unless there is a good seal between the mask and the wearer’s face, many aerosols and droplets will leak through the top and sides of the mask . . . ."

**Which fit issues have you experienced with masks you've used?
( I found that KN95 masks fit my face well. )