Mosquito repellent principle: The bracelet achieves a mosquito repellent effect by imitating the annoying sounds of female mosquitoes, such as the sounds of male mosquitoes and dragonflies. In nature, all blood-sucking mosquitoes are female mosquitoes, and they are all in the fertile and egg-laying period. In this price range, female mosquitoes will avoid male mosquitoes to avoid secondary pregnancy. Therefore, simulating the sound of male mosquitoes can achieve mosquito repellent effect. Product features: purely physical, non-chemical mosquito repellent, safer, more environmentally friendly, safer and healthier. It can be worn by the elderly, children, pregnant women and pets. The product is portable and can be worn indoors and outdoors. (at the beach, park, camping, mountaineering, fishing, etc.). Product name: ultrasonic mosquito repellent bracelet. Product model M1 Ultrasonic Mosquito Repellent Function Input 5V/1A Output 34Hz-70KHz Battery capacity 90mAh Charging time: approximately 30 minutes Battery life: 130 hours Product color black.white Note: The data is manual measurement, please allow 1-3cm error, due to differences between the light and screen, there will be a certain color difference, the specific received in kind shall prevail.