Specifications: Main control chip: Telink8266 Vibration: Silence / Vibration Waterproof level: IP67 Compatible systems: Android 4.4 and above, iOS 8.0 and above Features: heart rate, blood pressure, blood oxygen Screen size: 0.96 inches HD color screen TFT 80*160 Screen type: TFT Battery type: polymer lithium battery Battery capacity: 90mAh Charging method: dedicated USB charging cable Charging time: about 2H Life time: 10 days of use (depending on frequency of use and frequency of push content) Data storage: 7 days of historical data of bracelets; over 7 days of data retention APP Control method: single touch Appearance material: front shell: PC, rear shell: ABS+PC, wrist strap: environmental protection TPE Color: black, blue, red Packing List: 1*M4 Smart Bracelet 1*Charging Cable 1*Instruction