The grow flow expansion kit includes 12 growing modules, each consisting of around a 2-gallon pot with fittings, an inner bucket, and all necessary connectors and tubing. Each pot features a concave bottom with multiple drain holes for better water flow. Please note that a control unit and reservoir (sold separately) are required to use this expansion pack. This growth flow Expansion Kit is part of the most efficient ebb & flow system on the market. You can connect up to 24 growing modules to a single 5-gallon system and up to 48 modules with the 2-gallon system! You can also build your own system from the ground up by purchasing all the components individually.