(3 Pack) 4 in 1, Multi Function Pest Repeller, With LED Night Light, The Most Powerful Pest Controller. Made in Taiwan. (3) Electro-Magnetic Wave: Uses an intermittent varied physical signal to emit a magnetic-vibrating wave, passes by connected power or ground lines that makes pests hiding in the walls uncomfortable and non-viable in order to repel them effectively. Ultrasonic Wave: Uses a high pitch sound that is unheard by humans but frightening to mice. The sound attacks the pests continuously in order to repel them effectively. The unit uses the vibrating magnetic wave and the pulsed supersonic wave to effectively attack mice and pests giving them no where to hide. The unit uses the super powerful two-emit dual speaker to create auto-sweep ultrasonic wave. It is effective up to 2,100 square feet. For maximum effectiveness, install a pest repellent in each separate room. Durable; Low Energy Cost; Non-Chemical; Harmless to Human, Pets, Household Electric Products & Computers; With EPA #074132-TWN-001