Cultiwool Block 4'' x 4'' x 2.5''Cultiwool blocks low density rockwool for fast rooting from plugs. From the melting of the basalt, until the transformation to germination plugs or growing blocks, everything takes place under close supervision. Doing so gives Cultiwool the opportunity to control the entire chain, and that makes our products more uniform, firmer and more productive. Cultiwool Features: Superb air to water ratio A fibre structure that holds water longer Less resistance