Screen Size 1.3 inch TFT Screen Operation Capacitive Touch Screen Wrist Strap Length Perimeter 5.5 - 9.5 inches Motion Sensor 3D Gravity Acceleration Sensor Heart Rate Sensor Second Generation Dyanmic Heart Rate Sensor WaterProof Level IP67 Recharging Current Within 5V 2A Battery Capacity 150 mAh System Requirement Andriod 4.4 and iOS9.0 and above Transfer Method Blutooth 4.0 Use Temperature 0 - 40 *C S7 Smart Watches: Ultra Thin Body: The all- metal casing uses a CNC drilling process to create an ultra thin body, and the one piece design makes the bracelet more compact. Personalty Strap: Stylish and Delicate buckle, soft matte texture strap, unique breathable wicking groove design more comfortable to wear. 1.3 Inch HD Display: Mainstrean curved glass grinding technology, New G + F comprehensive glass bonding process sensitive operation without sturdiness.