Made in Denmark since 1969, Grodan stonewool is known the world over for its quality, consistency, ease of use and performance. Seeds or cuttings are started in these large Grodan Gro-Blocks and, once rooted, the blocks are transferred to a larger stonewool slab. Gro-Blocks can also be planted directly into containers for soil gardening. This is a strip of six 4"x4"x4" Gro-Blocks, each with pre-formed holes.