This listing is for (4) Units. Bubbles the Fish II Pediatric Mask. PARI Bubbles The Fish II Pediatric Nebulizer Mask fits all PARI LC nebulizers, plus the PARI Vios (Pediatric) and Trek S aerosol delivery systems, and older PRONEB Ultra II pediatric compressor nebulizers. Also compatible with non-PARI "bottom-loaded" nebulizers using included elbow adapter. Optimizes delivery by directing aerosol towards the patient's mouth; and the character design -- with a soft, flexible materials and soft edges -- makes treatment comfortable and fun without pinching or irritation. Bubbles includes a wide elastic band with interlocking tabs to provide your child with a perfect fit. Designed specifically for use with PARI nebulizer kits, but still compatible with most standard kits "Bubbles" is the most popular child aerosol mask on the market today Aerosol mask designed especially for children to have fun with treatments Unique front-loading system minimizes aerosol wastage