Bad news if you wear one of those neck gaiters as a face mask. Turns out they don’t do much to protect you. A new study at Duke University looked at 14 different types of face coverings to see which ones block the most particles. Overall, they found N95 masks work best and block the most particles. Disposable surgical masks were almost as good. And homemade cotton masks with multiple layers did well too.

Knitted masks with bigger holes like a scarf didn’t block as many particles, for obvious reasons. Bandanas didn’t do well either, partly because they’re single-layer. But the worst mask by far were neck gaiter masks. They might even make people more likely to spread the virus, because they create even smaller droplets that stay in the air longer.