You'll find everything you need to start a windowsill garden with the Hydrofarm® Jump Start Windowsill Heat Mat and Tray Kit. It includes two 12-cell pellet greenhouses that allow you to take charge of your seed starts. Each mini greenhouse features 12 peat pellets and a vented dome to create the perfect environment for your plants. The kit also comes with the Jump Start Windowsill Heat Mat. This mat fits perfectly underneath the two greenhouses, and is the perfect size for small growing spaces. The heat mat improves germination by warming the root area 10-20°F over ambient temperature. By warming the roots, you'll increase your growing success. The mat is 3" x 20".