Luoov Brand Smart Bracelet Bluetooth Passometer Touch Screen Fitness Tracker Health Wristband Sleep Monitor Smart Watch For Android IOS Iphone (BLACK) CompatibilitySamsung HTC Huawei Nokia Etc all kinds of smart device which have bluetooth function, android 4.3 and above or IOS 9.0 and above,bluetooth 4.0 and above IP67 Waterproof Heart Rate Monitor Standby time:It can keep working as long as 15 days if you don't use it,normal, it can work as long as 7 days if you use it Multi function:time display,step counting,distance measure,calory consumption counting,calling display,message remind,sleep status monitor,shaking and take photo to help your phone,etc We promise: 30 days return and exchange, 12 month warrantly. So please be secure to purchase