This Chasing Windmill is one of the most humane deterrents that you'll find. Moles disfigure lawns with their tunnels, kill young plants by nibbling on their roots and eat the gardener's best friend, the earthworm. The spinning blades of the Chasing Windmill drive them away by sending vibrations through the ground. Moles can't stand this, and soon leave your yard in search of a more tranquil environment.. It is a simpler, more effective and more humane than chemicals and poisons and is completely silent, never needs batteries.. Covers nearly 20,000 square feet (up to 75 ft in all directions) and extremely effective on soils with clay content (like moles love).. Zinc-plated steel. Blades 18"L, 3 lb.. Assembly is required, and an additional mounting pole required (NOT INCLUDED) - For best results, install with 8 ft of 1/2" steel rod. May be installed on shorter rod, but it may only cover a smaller area. . Ground rods are available at any building supply outlet, electrical supply houses and many hardware stores. For best results, install with 8 ft of 1/2" steel rod "grounding rod". Less effective in sandy soils where vibration doesn't travel as far. Does not work on groundhogs or voles. Helpful Tip: The windmill unit WILL NOT fit snugly on the grounding rod. The fit is loose to allow for vibration from the pole into the ground.