Ultra-Accurate: Electronic spirometer with differential-pressure-type sensor measures 2 parameters PEF & FEV1. Indicator & Customize Normal Expected Values: Spirometer with large green backlit LCD screen which automatically displays test values. You can set up your personal expected value. Smart Software Analysis: Digital peak flow meter connects to tracking app via Bluetooth. Once connected, data is automatically synced to the mobile phone. You can share your results with your caregiver through the tracking and analysis app. Portable & Rechargeable: Personal pocket spirometer is rechargeable and includes a USB cable for convenient charging. A single full charge lasts over 6 months. Please charge the device for about 2 hours before first use. When the battery icon appears, it needs to be charged. 2 Types of Mouthpiece: The peak flow meter stores test records, each with a timestamp. You can set the time before testing. The spirometer comes with 2 types of removable and washable mouthpieces. Choose the one that is more comfortable and clean it with alcohol to remove contaminants.