Grodan Rockwool Cubes - 1.5"x1.5x1.5" - Sheet of 98 cubes1.5"x 1.5"x 1.5" Grodan Stonewool ( rockwool ). Made from molten rock spun into cotton candy-like fibers and then compressed into cubes. Grodan is unique by making different types of fibers. Grodan is made to support the requirements of the plant in different plant stages. Grodan has a tremendous capacity for absorbing nutrient solution while retaining plenty of oxygen for rapid plant growth. Seedlings started in cubes are easily transferred to blocks or onto slabs, if desired. Seedlings or cuttings started in the Grodan cubes can also be transplanted into more traditional planters and growing mediums. Check out my other items! We ship fast Monday through Saturday on non-plant items!