6pcsPack Ultrasonic Electronic Cockroach Mosquito Pest Reject Repeller, US Plug 1. Pest control uses ultrasonic frequency (22-65Khz) sound waves to drive pest and rats away without killing them. 2. Ultrasonic repeller is non-toxic repelling device and the ultrasonic frequency is inaudible to humans and pets (Except rodent-like pets such as hamsters). Completely harmless to human health. 3. Unlike glue ant traps, mice sticky traps & pest poisons, ultrasonic repellents won''''t leave a messy to clean up. Plug in the electronic mice reject and let it do the rest. Please install about 30cm away from the floor. 4. The Ultrasonic pest repellent is effective for an area up to 50-80sqm. However, as the ultrasonic wave is Fast Decay & Poor Penetration, it can''''t cross the wall. 5. Injure or kill household pests such as rodents and insects including cockroach, mosquito, rats, etc. Widely use in home, warehouse, hotel, hospital, etc. 6. Note: The US Plug only support the flat plane type socket (Not included), do not support the concave notch type socket (Not included).