​The One-Way Valve Mouthpiece is a disposable paper mouthpiece featuring a one-way valve for expiratory-only testing. The plastic valve has been designed to provide low air resistance. This mouthpiece features a 1 3/16 inch outside diameter, the same diameter as our popular paper mouthpiece #162600.One-Way Valve for expiratory-only testing Strong, durable construction Special design provides low air resistance
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