The CubeCap? is one of the first environmentally safe solutions available. In addition, you are able to recycle and reuse the CubeCap? thus saving on costs. The CubeCap? deprives the cube of its light by reflecting it back up towards the plant and away from the top of the block. The CubeCaps? patented technology allows the necessary air exchange by way of its unique elevated, vented design. Designed for use with 4 in and 6 in rockwool blocks.