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 10-20°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
7.3 Watt
    Features:
3" x 20"
UL listed
Includes power cord
7.3 Watt