Rapid Rooter Grow Plugs are a sponge like material, all natural soilless organic grow plugs made of composted tree bark and organic materials. These biodynamic plugs are perfect for seedlings or cuttings. Transplant plugs in soil or soilless hydrogardening applications. Grow Plugs are manufactured with a proprietary composting method and contains natural beneficial fungi from this advanced composting biotechnology. Seedlings and cuttings grown in Grow Plugs will be able to transplant days ahead of plants started in Jiffy 7, Rockwool, Oasis, or Pro Mix. Grow Plugs are biodegradable and 100% organic. Includes 10 x 20 inch tray.Rapid Rooter's technology produces a unique matrix of composted organic material bound together by plant-derived polymers. Rapid Rooter is created through a scientifically controlled process that produces large populations of beneficial microbes in the plug media. These naturally occurring beneficial microbes colonize young roots and help young plants to resist disease while maximizing nutrient uptake. Rapid Rooter plugs are fortified with General Hydroponic micronutrients for abundant root growth. The optimal air-to-water ratio within the plug matrix causes explosive early root growth. Use Rapid Rooter for robust early rooting that promotes explosive plant growth.plugs are 1.5 inches (38 mm) across the top and 1.75 inches (44 mm) tall.