Stonewool is recognized the world over as the ideal hydroponics growing substrate. Seeds or cuttings are started in these Grodan Gro-Blocks and, once rooted, the blocks are transferred to a larger stonewool slab. Gro-Blocks can be planted directly into containers for soil gardening as well. This is a strip of eight 3"x3" x2.5" wrapped Gro-Blocks, without pre-formed holes. Grodan stonewool is known for its quality, consistency and performance. Gro-Blocks are similar to a ‘plant container’. Need a 3” pot? Then choose a 3” Gro-Block. Small plants can be fully grown in our larger Gro-Blocks.  Come in packs labeled with instructions.