SunPack Tray Black 10 x 20 IN are extra-strength seedling trays. These trays are sturdier than most trays, ensuring you will get multipe season of use. The SunPack 10x20 tray is a standard size, so you can still use your humidity dome and heat mat. With reinforced sides, they are easy to move from the house to the greenhouse or garden. These trays also feature deep-channel ridges on the bottom for better drainage and stability.