In the explanation of how to use it, it is said that the hook is hooked on the folds inside the mask, but I use it as it is. With this cover, it's comfortable that the inside of the mask doesn't cling around your mouth. In addition, I think it is epoch-making to be able to apply lipstick because the mouth does not stick directly to the mask.
It's a little chilly at first, but you can get it right away. After all, it feels like there is a space between the mask and the mouth.
Since it is made of plastic, it is hygienic where you can quickly wash it with water if it gets wet with sweat.