This planter is made out of one piece with a double bottom so as to provide a water reservoir and a water level indicator. The roots of the plants go through the small openings in the double bottom accessing as much water as they need, but the water level indicator helps prevent the planter from being over-watered. Due to this system plants grow much better and live longer. In addition, the planter comes with lockable wheels--for easy rolling around. It can be used both indoors and outdoors - great for moving sensitive plants indoors during the winter. With its large water capacity this unit can also be left alone for more than a few days - take a 2 week vacation.