Plagron Euro PebblesPlagron Euro Pebbles: superior drainage for high yield hydroponic crops. A high quality inert hydroponic substrate made from pure, salt free clay. This clay is baked in an open kiln until it achieves its characteristic irregular shape, resulting in ceramic pebbles that are firmer, cleaner, and more stable than other options on the market. Thanks to its low water retention capacity and high porosity, Euro Pebbles allows total control over nutrition,