We have been using these masks since April or May 2020 when I found Mountainside Medical whenever we go out ie. Curbside grocery pick-up, curbside medication pick-up, etc. IN CONJUNCTION with the CDC recommendations of masking, 6-foot distancing, avoiding large crowds inside restaurants, etc and frequent handwashing. I had a few of a different brand of masks which my husband inadvertently used and the mask elastic ear-loop broke from the top of where the loop is connected to the mask itself and it happened as he was walking out from having received his 2nd Covid vaccine. I threw those masks out immediately because they couldn’t be trusted! So Mountainside Medical KN95 masks are the ONLY face masks we use. I like the design of these masks because by carefully pulling the lower edge down under the chin and fitting the top aluminum strip to the shape of our nose, there is a very nice fit even along the mask’s sides to prevent gapping along the sides. Fit is comfortable for me and my husband when we wear them. We change out to a new mask if we see any visible dirt or it gets difficult to breathe. We keep these masks as a ‘back-up’ in a zip-lock bags in both our cars’ glove compartments with the small Hand- sanitizers. I also have put a few in our ‘emergency kits’ in the trunks of our cars. Love the quality put into these masks!