The Garden Tray GT15 from American Hydrotech is a molded, three-dimensional tray made from recycled polyethylene for use in a Hydrotech garden roof assembly. An 18-inch-by-22-inch tray includes retention cups on the top side, drainage channels on the top and bottom, and perforated domes for ventilation and evaporation. Each GT15 has filter fabric laying across the bottom of the tray, which is topped with growing plants. When placed loosely over IRMA Stone Filter Fabric and Stryofoam insulation, a single tray covers 2.75 square feet.; 800.877.6125.