Non-Rebreathing Oxygen Mask with Reservoir Bag, Adult Model, Two Valves. One-way valve on the reservoir bag allows a higher concentration of oxygen to flow into the mask. PVC construction, elongated-style clear mask with a soft aluminum nose piece. Disposable - prevents cross contamination and eliminates cleaning requirements. Complete with 2.1 m (7') 100% PVC oxygen tubing and a polypropylene connector. Dual one-way valves on the side ports permit exhaled air (carbon dioxide) to exit the mask and prevents outside air from entering mask. Sold as 50/Case