Ultra-Accurate: Electronic spirometer with differential-pressure-type sensor measures 2 parameters PEF & FEV1.Indicator & Customize Normal Expected Values: Sonmol Spirometer with large green backlit LCD screen which automatically displays test values, you can set up your personal expected value.Smart Software Analysis: Our digital peak flow meter can connect to our tracking App via Bluetooth. Once the Bluetooth connects successfully, the data can be automatically synced to the mobile phone. You can share your results with your caregiver through our tracking & analysis ePEF App.Portable & Rechargeable: The personal pocket spirometer is rechargeable and the package includes a USB cord, enabling you to carry it anywhere. A single full charge for more than 6 months of use. *Please charge the device about 2H before first use. When the device displays the battery icon x, it needs to be charged.2 Types of Mouthpiece: The peak flow meter can store test records, and each record has a test time. you can set the time before your test. Our spirometer with 2 types of removable and washable mouthpieces. You can choose the more comfortable one and simply wipe it with alcohol to clean it, with no worries about residual contaminants.