Bluetooth Fitness Activity Tracker Heart Rate + Sleep Monitor Wristband Black TR Specification: Basic Parameters: Name: Smart Wristband Material: High Quality Rubber(Comfortable feel) Color: As pictures shown Size(Lxw): 25 x 2.1cm Display Size: 2.2 x 1.5cm Weight: 28g(Unpacked) Waterproof Rate: IP67 Working Temp: -20~+45 Operating Temp: -40~+45 Hardware Parameters: Charge Method: Standard USB charging Display Size: 0.49 OLED Battery: 100mAh polymer battery Standby Time: over 4 days Synchronized with the following devices: PC terminal: WindowS XP, Vista.7+