Rockwool cubes are approximately half-inch square in size and have high water retention. Be sure to use low to no mineral water (pure water such as reverse osmosis) and reduced fertilizing when using this product. Very useful for growing phragmipediums, miltonias, oncidiums, zygopetalums and odontoglossums. Lots of airspace between cubes. Can be blended with spongerock and/or charcoal for more drainage. Small bag fills +/- 3 one-gallon plant containers. Large bag fills +/- 23 one-gallon plant containers.For large view of cubes, click here.