I think the radius is not as great as indicated. We have distributed 3 pieces around the house, and in the vicinity of the equipment the hills have disappeared. It must now manufactures a fourth device, as a corner always shows mole activity. But then hopefully calm. It takes really a few weeks, and the activity of the mole can increase only once. Patience paid off for us but out.
Addendum after a few months use: I'm excited. In all gardens around hills can be seen, only with us the lawn is continuously flat and green.
