Unlike some other pebbles on the market, the non-uniform shape of Plant!T GMC45L clay pebbles result in an increased surface area that leads to better aeration and greater water retention in your garden. They are also tumbled in the manufacturing process to give them softer edges that are kinder to new root growth when transplanting. These clay pebbles are pre-cleaned, made from 100 percent natural clay, pH and EC stable, and will not float once fully wet. They can be used for aeration, drainage and decoration. Use in flood and drain systems, deep water culture (DWC) systems, drip feed systems, and aquaponic systems.