The unique size and structure of Gold Label HydroCorn creates a growing medium that is the substrate of choice for hydroponic professionals. The clay pebbles are baked in an open furnace using high grade clean fuels to ensure the absence of heavy metals and other contaminates, and are also RHP Certified for Horticulture. They are uneven in shape, which provides an ideal surface for roots and beneficial bacteria, and its porous structure has a high water capacity. Suitable for both ebb and flow and top irrigation systems.