Cultilene 6x6x4 Block w/ Optidrain (64 pieces per case)Cultilene Blocks have an optimum air water ratio for healthy root growth and allow for great continued rooting thanks to the extremely even distribution of water and EC. These blocks have an excellent water absorption and (re)saturation rate and feature the exclusive Plant Comfort fibre structure which has a lower density of resistance during rooting with no loss of firmness. All blocks except the 3x3x3 also have the Optiplus feature, which is a