A special porous ceramic material allows these 6" pots to wick water and keep plants moist. Molded ridges on the bottom of each pot fit into the bottom of the humidity tray used in our indoor plant gardens to make a highly effective growing environment for indoor plants. Smart Pots work with our Tabletop Humidity Tray, Tabletop Plant Light, and Window Plant Table Ideal for indoor herb gardens and moisture-sensitive plants Proven to grow healthier plants Set of 4 pots Made of unglazed terra cotta Pots wick water from below Drain hole stays above water, allowing air to circulate 6" diameter, 1 quart soil capacity Protect from freezing temperatures