Gold Label Hydro expanded clay pebbles have a very solid outer ceramic layer, which limits the uptake of water.
They are ideally suited for intense irrigation hydroponic styles of growing.
Be aware that although the pebbles are very dense, they can float in deeper ebb-flow systems.
As the pebbles are round and have a very even shape, they leave a lot of space for oxygen in the root system. The closed surface of the pebble makes it hard for the roots to attach, enabling easy cleaning and re-use of your substrate.
Always wash thoroughly before use!