The Grodan 6" cube sometimes refered to as a Hugo Block . The cubes are a sterile hydroponic growing medium with a pre cut 1.5" hole to hold the seedling or cutting you are repotting. Some growers will use the use the cubes till roots show out pf the bottom and then re-pot into a larger pot or system. Other growers growing small to medium sized plants will use the 6" cube to house their plants until harvest. The Grodan cubes need to be conditioned or soaked before planting. See BELOW for a great video on how to condition different sizes of cubes.