The principle of mosquito repellent: the bracelet achieves the effect of repellent mosquitoes by imitating the sounds of female mosquitoes, such as the sounds of male mosquitoes and dragonflies. In nature, the bloodsucking female mosquitoes are all at the stage of conception and spawning. At this price, Female mosquitoes will prevent male mosquitoes and avoid secondary conception. So the sound of male mosquitoes can achieve mosquito repellent effect. Product features: Pure physical mosquito repellent, non chemical mosquito repellent, safer, safer, more environmentally friendly, and healthier. Can be worn by the elderly, children, pregnant women and pets. The product can be worn indoor and outdoor (sea, park, Camping, climbing, fishing) Specifications: Product Name: Ultrasonic Mosquito Watch Product model: M30 Function: Sonic mosquito repellent Input: 5V / 0.5A Output: 34Hz-70KHz Battery capacity: 80mAh Charging time: about 30 minutes Endurance working time: 150 hours Product color: black, white, blue, pink Single package size: 32 * 52 * 78mm Total weight (including packaging): 36.5g Packaging: 210 * 280 * 430mm Package Included: 1 * mosquito repellent bracelet 1 * Charging cable 1 * User Manual