We live in a small town over-run with gophers and moles. It has been an endless struggle keeping the little pests at bay. We don't like using poisons or traps because of pets in the neighborhood. These electronic repellers are just what we needed.Properly installed, they are supposed to have a range of about a 30 yard radius, which is perfect for our front yard. Each unit comes in 2 pieces: a metal stake with sound transponder in it, and a head unit which contains a solar cell and rechargeable batteries inside. In the ground they make a little buzzing sound, but it is intense under the ground. The theory is that tunneling pests will be encouraged to go elsewhere by the unpleasant sound underground. I trust that these units will be a good aid in keeping the yard clear of rodents.