Gardeners can see all the benefits of growing with a Smart Pot even if they grow in trays, thanks to the Smart Pot Tray Liner! This soft material allows more air to reach the growing medium and roots, improving drainage and keeping the root system from overheating on hot days. Plant roots also benefit from their natural tendency to grow into soft surfaces like the Smart Pot Tray Liner, becoming thick and healthy instead of circling the inside of the pot and becoming root-bound. This liner will fit any tray up to 4' x 4' x 12".