This horticultural stonewool, which is made in Denmark, is used the world over by both hydroponic and soil gardeners. Growers can start cuttings and even grow plants to maturity in this large Grodan Gro-Block. Holes are a perfect size for any 1.5 inch starter plug. Gro-Blocks can be planted directly into containers for soil gardening as well. There are 64 single 6"x6"x6" Gro-Blocks with a pre-formed holes in a case. Instructions are on label.