Grodan Grow Cubes are 1/2" x 1/2" loose rockwool blocks. They are mainly used for container growing. You can mix them in with any other medium that you would like (such as perlite/vermiculite, coco peat, etc) or just use by themselves. They have an excellent water to air ratio for fast growth. They come in 11 gallon bag, 23 gallon bag, and 32 gallon box.