This F4 Smart Watch - Black and Red has multi-function, like heart rate monitor, simulate blood pressure, instant messaging. This smart watch is ultra-light, comfortable and precision laminated. Watch Strap is made of strong and soft Nano TPU85 to avoid sweating during sports and sports, and to ensure the durability of smart watches. The adjustable strap to any size of length fits your wrist. The best partner in daily time and outdoor sports activities.