Gold Label Hydro Clay Pebbles are manufactured using a mix of the best quality pure clay and are baked in an open furnace using high-grade clean fuels. This guarantees the absence of heavy metals or other contaminants. Gold Label Hydro carries the RHP for horticulture quality certificate. Gold Label Hydrocorn is the inert hydroponics substrate of choice for professionals. It provides stability and the unique uneven shape of the pebble is an ideal surface for roots and beneficial bacteria. The porous structure has a high water capacity and is suitable for both ebb/flood and top irrigation systems.