M21 Ultrasonic Mosquito Repellent Bracelet with Step Counter & Clock & Temperature Function 1. Function: Mosquito RepellentElectronic WatchSports Step CounterTemperature Measurement 2. Principle: The bracelet achieves the effect of repelling mosquitoes by imitating the sounds that female mosquitoes hate, such as the sounds of male mosquitoes and dragonflies. In nature, all blood suckers are female mosquitoes, and they are all in the period of conception and laying eggs. At this stage, female mosquitoes will avoid male mosquitoes and avoid secondary pregnancy, so simulating the sound of male mosquitoes can achieve mosquito repellent effect. 3. Pure physical mosquito repellent, not chemical repellent, safer and more secure. It can be worn by the elderly, children, pregnant women and pets. 4. The temperature detection needs to be worn for more than five minutes, and the detection data is more accurate 5. Charging interface: mirco5v1A 6. Three-speed frequency conversion, wider adjustment applicability 7. Battery capacity: 200mAh 8. Size: strap length 260mm, width 22mm 9. Note: The bracelet adopts bionic waves, which can effectively repel mosquitoes. However, the species of mosquitoes in different places are different,there is no guarantee of complete repelling of mosquitoes