NUTRIFIELD HYDRO CLAY HYDROPONIC GROWING MEDIUM NF GERMAN MADE GERMAN MADE Nutrifield® Hydro Clay starts with the highest grade natural clay following a strict grading formula and is assembled via granulation method. By following this process we guarantee that you get a more consistent spherical shape and size with a more uniform and rigid structure that resists breaking. You get a consistent 8-16mm round shape that is rigid and made from 100% freshly mined raw clay material free of impurities and ready to use straight out of the bag.