Stonewool Macroplugs are a sure bet for optimum germination. They start as basalt rock and chalk that is melted, spun into cotton candy-like fibers, and finally compressed into plugs. Their fibrous structure creates an ideal air-to-water ratio which contributes to robust root development throughout the entire plug. If you're ready to experience phenomenal growth with premium rockwool - the Grodan Macro Plugs are your gateway to better growing.