Ring of 18 interconnected vertical plastic tubes filled with water, that provide a warm summer-like growing environment. Releases 1.8 million calories of heat when the water freezes. Warms the soil at night. Protects against frost down to 16?F. Use to plant 2 months ahead of normal planting time. Each Wall-O-Water encircles an 18" diameter area, just right for tomatoes, peppers, eggplants, melons and other heat-loving, frost sensitive plants. These cost-effective mini-furnaces can be reused season after season. Damaged sections can be fixed with repair inserts.