Main Features: The principle of mosquito repellent: The bracelet achieves the mosquito repellent effect by imitating the sounds of female mosquitoes, such as the sounds of male mosquitoes and dragonflies. In nature, the blood-sucking female mosquitoes are all in the pregnancy and egg-laying period. In this price range, Female mosquitoes will avoid and male mosquitoes to avoid second conception. So simulating the sound of male mosquitoes can achieve mosquito repellent effect. Product features: pure physical mosquito repellent, not chemical mosquito repellent, safer, more environmentally friendly, more assured, and healthier. The elderly, children, pregnant women and pets can wear it. The product can be worn indoors and outdoors (by the sea, parks) , Camping, hiking, fishing). Specifications: Name: Ultrasonic Mosquito Repellent Bracelet Model: M1 Function: Ultrasonic mosquito repellent Input: 5V/1A Output: 34Hz-70KHz Charging time: about 30 minutes Endurance working time: 130 hours