Please pair the fitness tracker with your phone via the VeryFitPro app, (not via your phones Bluetooth settings)Please charge your activity tracker for at least 10 minutes to have it activated before initial use. Please note: Please wear your fitness tracker a little loose and clean and dry it after sweating to prevent discomfort and ensure the best wearing experience.Mobile phone system requirements: iOS 8.0 & above Android 4.4 & above Bluetooth 4.0 & aboveModel no.: ID152Sync: Bluetooth 4.2Battery Capacity: 90mAhWorking Voltage: 3.7VWorking Temperature: -20?-40?Weight: 0.85oz(24g)Water Resistant Rating: IP68Working Time: 5-7 daysUSB Charger Requirement: DC USB port(5V-500mA)Charging Time: 1-2hr(s)