This set of two pack ultrasonic pest repeller is a must have around the house, out buildings, sheds and barns. It is a very easy way to keep all types of pest at bay and away. It comes two to a pack, super easy to set up and start using. The sensors can be set for different frequency for use on different pests. The repellers can be used on as small as a flea or as large as a mouse or spiders. Does not harm the pest only keeps them away, do environmentally useful. Easy to use and safe for all pets and children.