PROS: These masks fit very well, have an adjustable strap, and are more breathable than other KN-95s I've used. They're breathable enough to use at the gym for light to moderate activities, such as weightlifting, stationary bikes, or moderate walking on the treadmill. Others I know also use them for more intense cardiovascular activities.
CONS: They are not very nice with glasses. Because of their structure, air can be pushed up into your eyes after it leaves the filter.
OVERALL: I highly recommend these masks.