Gold Label Hydrocorn the ONLY RHP certified clay-pebble substrate • Hydrocorn 8-16mm • Hydrocorn (XL) 16-25mm Hydrocorn is irregular shaped, this allows roots to get a grip and produce more side hairs. Because they produce more side hairs, they are able to absorb more elements. A stronger root system creates a healthier and better producing plant. HYDROCORN-RHP pebbles are baked in clean fuels, therefore they are food grade and RHP certified. We are proud to say that our HYDROCORN products are the only clay pebbles on the globe with RHP for horticulture certification! Gold Label Hydrocorn clay-pebbles are porous and able to absorb about 15% of water of its own weight, so therefore they are much more forgiving for the users.