addition mouthpieces for Buhl spirometer (250 pieces) disposable cardboard Inexpensive spirometer for screening large populations. Subject blows into disposable mouthpiece. Indicator registers forced vital lung capacity up to 7 liters. Reading stays at maximum until reset. Use as an incentive exerciser for respiratory problems. Weighs 6 ounces. Spirometer comes with 100 mouthpieces. Product photo may not exactly match the product offered for sale. Please refer to the product description.