First, all masks and PPE do is reduce the chance of transmission/infection/inhalation, none 100% prevent it by themselves. For 100% protection (well technicall

First, all masks and PPE do is reduce the chance of transmission/infection/inhalation, none 100% prevent it by themselves. For 100% protection (well technically as close as we can get) typically you need a positive pressure suit and a self contained breathing device. Anyway, while you are technically correct the virus itself is smaller than the mask's ability to filter. What people are protecting against is the droplet transmission and, for that usage, the N95 masks are effective. The CDC, NIH and many scientists have stated they are even appropriate for health care workers in direct contact with patients because it will stop the primary means of the transmission when used with other proper PPE like glasses (or more properly in healthcare, face shields), gloves and gowns. Of course, an N95 mask (or any filtering level, P100, N100 etc) won't stop you from getting a virus if you touch a contaminated surface then touch your face etc. But if someone is coughing near you an N95 mask is acceptable to reduce the transmission risk.