These high quality German sourced Clay Pebbles are clean, pH neutral, pH stable and are good to use in all types of systems from flood & drain to dripper system. Even hand watered pots! They can also be combined with other growing media such as coco, soils or cellmax to improve drainage and structure. Can be reused once if you use Cannazym whilst growing and Oxy-Plus to clean them with after your crop is finished.