The Cultilene Rockwool cubes, plugs, and starter sheets are by far the best on the market. They offer superb air to water ratio and a fibre structure that holds water longer. Less resistance for the roots to grow in results in stronger roots.
Cultilene Rockwool also encourages faster initial rooting and its firmness is guaranteed. Grow Cubes are 1/2 cubes of Rockwool which can be mixed with other loose media. Sold by the case.