Seedling heat mat 3"x20" 7.3w. 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 10-20a°f 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. features: 3" x 20" , ul listed. includes power cord.