Jump start windowsill & heat mat & tray kit, includes two 12 cell pellet greenhouses that allow you to take charge of your seed starts, each mini greenhouse features 12 peat pellets & a vented dome to create the perfect environment for your plants, 3" x 20" windowsill heat mat fits perfectly underneath the 2 greenhouses, perfect size for small growing spaces, heat mat improves germination by warming the root area 10-20 degrees fahrenheit over ambient temperature, by warming the roots.