Hydrofarm's windowsill heat mat is perfect for veteran growers, beginners and children too. It is the perfect size for small growing spaces and improves germination by warming the root area 10 to 20 degree Fahrenheit over ambient temperature. By warming the roots, you increase your growing success, as this mat will maintain a controlled temperature all season long. If you ever dreamed of growing a windowsill container garden but found the area just a bit too drafty, add this heat mat and you'll be ready to get growing. Heat matPerfect for veteran growers, beginners, and childrenPrefect size for small growing spaces, and improves germination by warming the root area 10 to 20 degrees F over ambient temperatureUL listed