This mask is for use with nebulizer treatments. The mask focuses the nebulizer treatment to the mouth and nose, making it easier to take a treatment without having to hold the nebulizer between your lips. The included elastic strap helps you find the most comfortable fit. Also, this mask is made from soft, flexible plastic for added comfort. This mask only works for nebulizer treatments, and comes in a case of 50, fitting either a size for an adult or child.