This is a mouthpiece meant only for use with the Lumiscope portable Ultrasonic Nebulizer System. The mouthpiece has a two-valve system to ensure maximum efficiency of inhalation and to minimize medication waste. In practice, the mouthpiece expiration valve will open when you exhale, allowing your exhaled air to pass to the atmosphere, avoiding contamination of the device. During inspiration, the valve will close, maximizing the inhalation amount. Mouthpiece is sold individually.