In the past two years of the COVID-19 pandemic, we have been seeing dozens of mask types on sale in pharmacies and stores. The question is, which one is the best to use?

It depends on your situation, but health officials say it should cover your nose and mouth, and fit snugly so there aren’t any gaps on the sides of your face.

The U.S. Centers for Disease Control and Prevention (CDC) also says to pick masks with two or more layers and a nose wire to prevent air from leaking out the top. It suggests holding your mask up to check if it blocks light, which means the fabric will probably filter out more particles.

If you want added protection, experts also suggest wearing two masks or pairing them with a mask fitter to ensure they don’t leave any gaps.

It’s also important to find a mask that’s comfortable so you actually wear it, says Laura Kwong, an assistant professor in environmental health sciences at the University of California, Berkeley.

If supplies are available, people can opt for disposable N95 or FFP2 masks for personal use, the CDC says in updated guidance. Such masks are considered most effective at blocking virus particles. The agency had previously said N95 masks should be reserved for health care workers, but supplies have since expanded. FFP2 is the European standard for particulate respirators, similar to the U.S. standard of N95, which filters out 95% of aerosols.

For people interacting with certain groups, such as those who are deaf or have hearing difficulties, there are also clear masks or cloth masks with clear plastic panels. Health officials say transparent medical masks should be prioritized for health workers and patients who need them.