Cultiwool Block 6'' x 6'' x 6''Cultiwool blocks low density rockwool for fast rooting from plugs. Cultiwool is a leading manufacturer of rockwool a popular grow medium that is spun from stone. The uniformity and direction of the fibers facilitate strong root structure as they create the ideal level of resistance for the roots to grow into. Cultiwool manages the entire process of rockwool production from the melting of the basalt to the end product germination plugs or growing