Mosquito Repellent (4 Pack) Mosquito Repellent (4 Pack) Ultrasonic Mosquito Repellent - This is our advanced version. Using the principle of ultrasonic waves, the frequency is changed to stimulate the auditory system of mosquitoes and other pests, making them unbearable and uncomfortable. Wide Coverage - Each ultrasonic electronic insect repeller is effective for a large area, up to 800-1300 feet. Please note that ultrasonic waves cannot pass through walls. Although our insect repellent works well, if you have a large insect infestation, we recommend placing our insect repellent in every room. Environmentally Friendly and Safe - This product is non-toxic and environmentally friendly. Environment, our insect repeller is 100% safe and effective, the ultrasonic frequency emitted by this machine is inaudible to humans and pets. Safe for children, families and pets. However, if you have a hamster pet at home, please do not use this ultrasonic mouse repeller. Easy to Use - This machine should be installed 80-120 cm from the ground. Vertical to the floor and plugged into an electrical outlet. It can be directly plugged into an AC 110V power outlet (power range: AC 90V-250V frequency: 50-60HZ). Commonly used in homes, warehouses, shops, hotels, hospitals, offices, etc. Large areas may require multiple devices.