Health officials are strongly suggesting people reconsider their mask options as the COVID-19 virus continues to mutate. And a three-ply mask is much more effective in shielding people from infection. (You can, of course, wear a cloth mask on top of one of those. Officials are just urging people to not rely on cloth masks alone.)

That advice—and the similarity between Omicron symptoms (such as fever, coughs, congestion, and body aches) and those of the flu—is once again renewing interest in N95 and KN95 masks. But it’s also resulting in a lot of confusion. Here are some things to consider as you upgrade your mask.

What’s the difference between a cloth mask, a medical mask and a N95/KN95 mask?

N95s (and some KN95s) are a type of respirator, filtering out both larger and smaller particles you inhale. Cloth masks, on the other hand, largely prevent the wearer from expelling respiratory droplets (though some are more effective than others).

There are two factors to consider: layers and fit. N95 and some KN95 masks have five layers of protection. A medical mask has three. And some cloth masks only have one.

You’ll also want to keep an eye out for gaps as you wear them. N95 and KN95 masks generally offer the closest fit, and therefore the better seal. Double masking, with a medical mask covered by a cloth mask improves the fit against most people’s faces for those options.

What’s the difference between KN95 and N95 masks?

N95 masks are the pinnacle of the face-covering world. They’re the ones used by medical professionals who are on the front line of COVID, as they’re especially effective in blocking airborne viruses, filtering out at least 95% of very small particles.

KN95 masks are largely imported from China and aren’t approved for use in medical settings, since they’re not regulated by U.S. officials. But a well-fitted KN95 is still more effective in stopping the virus than a cloth or disposable surgical mask.

What is a NIOSH-approved mask?

N95 masks have been around for years. And since 2018, the National Institute for Occupational Safety & Health (NIOSH) has worked with the Food and Drug Administration to approve the respirators. (KN95 masks are not regulated, so don’t carry NIOSH approval.)

It’s an ever-changing list of approved manufacturers, so, regardless of whether the sales listing boasts “NIOSH approved,” you’ll want to confirm that with the agency—since some companies that were once approved no longer are, but haven’t updated their marketing.

Find the extensive list of NIOSH-approved N95 masks at the organization’s website.

Can I buy an N95 mask now?

It was almost two years ago when many retailers refused to sell N95 masks to nonmedical personnel, reserving them for frontline workers. Things have changed since then.

You can now purchase an N95 mask fairly easily via Amazon and other sites. Just be prepared to pay a bit more for them. (And you’ll want to avoid the ones that have a ventilator, as health officials discourage use of those.)