Package contains only 4 mosquito repellent lamps Best ultrasonic repellents that quietly and effectively repel pests - If you are considering a non-chemical method, we recommend ultrasonic repellents, devices that emit constant noise at a frequency too high for humans to hear. These sound waves are designed to distract, harass and deter common household pests such as cockroaches, spiders, mosquitoes, ants and rodents. 100% SAFE FOR CHILDREN AND PETS , PROTECT YOUR FAMILY HEALTHY AND PEACEFUL -- Studies have shown that while cats and dogs can hear waves, humans and pets cannot hear ultrasound. Non-toxic, odorless and chemical free, safe for children, pregnant women and pets. How to use the ultrasonic repeller at home - Simply plug the ultrasonic repeller into an electrical outlet and it will start repelling pests when the blue night light comes on. The repeller should be placed where its noise will not be affected by walls and furniture. We recommend installing this repellent 30-50 inches above the ground for flying insects and 10-30 inches above the ground for crawling insects. 360 inspection of your home - effective coverage up to to 1600 square feet per pest control device. Since ultrasonic waves cannot penetrate walls and solid objects, it is recommended to use one piece, one set. 360 degrees without dead ends to protect your home. Widely used in homes, warehouses, offices, restaurants, supermarkets, hospitals, attics, etc.