Cultilene (Cultiwool) 6x6x4 Block w/ Optidrain (64 pieces per case)Cultiwool 6" x 6" x 4" Block w Optidrain (64 Blocks Case) Cultilene Cultiwools growing blocks are unique in the most efficient way. That has everything to do with the consistency of our products. Quick and easy uptake of water and the homogeneous distribution of water throughout the substrate are one of the most important features of a growing medium. Not only can you expect the highest quality stone wool in the market, but Cultiwool is also the first