Riddex® bed bug repeller keeps un­wanted nighttime invaders at bay...without chemicals! Device emits high-frequency, ultra­sonic, inaudible sound waves that reduce dust mite population and resultant allergy symptoms. Plug it in, turn it on and start seeing results! Harmless to pets and humans. Non-toxic and eco-friendly. UL-listed cord. 3 ¾" L x 2 ¾" W x 1 ¾" H.