This is our entry-level ultrasonic pest repeller, effective against mice and crawling insects. The Pest-Stop 500 uses fluctuating ultrasonic waves to cause auditory stress to pests. Direct plug-in design - use almost anywhere in the home. Covers 1 room. At least 500 sq. ft. Ultrasound does not penetrate walls or other solid objects, and is best positioned with an unobstructed 'view' of the target area. Fluctuating ultrasonic waves cause auditory stress to mice, rats and most crawling insects, which disrupts their normal behaviour patterns and makes it uncomfortable for them to stay in the same room as Pest-Stop 500. Safe and effective - no chemicals or traps. Will not affect humans, cats, dogs, fish or birds.