ROOT ROYALE Hydro Clay Pebbles are an environmentally friendly grow medium that can be reused over and over again! These clay pebbles have been fired in super-heated kilns causing them to expand and become extremely porous. These tiny holes and crevices inside each pebble hold and transmit extremely high amounts of air and water to your plant's roots, helping them grow bigger and faster, and making them perfect for hydroponic systems. And since these clay pebbles are pH stabilized, they won't release any additional minerals into your plant's nutrient stream. ROOT ROYALE Hydro Clay Pebbles are the most ecologically and economically sustainable choice for your growing needs!