The FloraFlex® Matrix System is a patent pending first of its kind Top Feeding Wicking System that provides the most even way to deliver water and nutrients to your potted plants. The Round Matrix System can be used with pots ranging from 7.5”-18” Diameters. The Matrix was notdesigned to be suspended above, but rather directly on top of, or touching the medium. There are two dimensions for each unit, the larger one is the outer diameter. Measure your pot and purchase the Matrix that fits inside of it. You will need a Matrix unit, the same size Matrix Pad(optional), and the correlating Matrix Circulator. Use with Open Flow Bubblers (not the Multi Flow Bubbler) for Maximum Pressure.