Totally inert = stable EC and pH Unique irregular shape and porosity which increases their surface area Reduced dust compared to regular pebbles pH 5.5-7.5 C 0.5 mS/cm² Water retention capacity 10% VitaLink Clay Pebbles offer strong structural integrity and enable good root aeration and development. They have a lower bulk density than clay pebbles of other brands, which means they are more porous and have a better ability to retain water. Our pebbles are also irregularly shaped, increasing their surface area compared to rounded pebbles thus allowing the plants more contact with nutrient solution. These premium clay pebbles have a very stable EC and pH, meaning they will not significantly change the pH of your nutrient solution, or leak undesired minerals into it. VitaLink Clay Pebbles are ideal for hydroponic systems, including flood and drain, multipot and drip-ring systems, as well as support media for deep water culture. Clay Pebbles can also be used to mix with other substrates to improve their structure, or to add a drainage layer in the bottom of pots. Our pebbles have been triple filtered to avoid smaller pebbles and dust, but we advise to wash them prior to use as there may be some dust created whilst they are in transit.