The Wall O’ Water Plant Protector wards off damaging cold temperatures as low as 10°F. Just fill the individual chambers with a garden hose to protect your seedlings and plants from cold and extreme heat. During the day, heat is absorbed in the side walls, moderating the temperature inside. At night, heat is released to the inside as temperatures get colder outside- even if the water freezes it releases heat! Thousands of home gardeners nationwide rely on Wall O' Water for plant protection. Measures 18" H x 18" diam. Holds 3 gallons of water.