This ultrasonic insect repeller emits invisible electromagnetic waves that can safely repel insects and rodents such as mosquitoes, ants, spiders, cockroaches, mice, etc. without causing death. It is made of durable ABS plastic, and because ultrasonic waves are inaudible to both humans and animals, they are very safe for children and pets. Simply plug it into an outlet to easily replace toxic chemicals. Please note that ultrasonic waves cannot penetrate walls.