This Ultrasonic Pest Repeller uses frequency shifting techniques which may prevent pests from developing an immunity. The device has an output of 140dB that can protect up to 280 square metres. The repeller may be effective against mice, rats, roaches, fleas, flies, crickets, silverfish, waterbugs, moths, ants, spiders and most other common pests. The ultrasonic frequencies used are out of the hearing range of humans and most household pets such as cats, dogs, fish & birds etc. A test feature down shifts the frequency output to an audible range. We make no guarantees that this device will solve your particular problem, but there are thousands of people who swear by them. -Supplied with mains plug pack and installation guide. -120mm dia x 75mm high