QRS Orbit™ Spirometer Disposable Mouthpieces (Z-5000-2608). All QRS spirometers use pre-calibrated, disposable mouthpieces. These mouthpieces are individually calibrated during production using the same equipment LDS Hospital uses to validate spirometers against the American Thoracic Society's Recommendations for the Standardization of Spirometry. 100/BX. Price per box.