General Hydroponics GH3213 CocoTek Mixed Brick, 24 bricks Includes 24 CocoTek Bricks ; Cocotek compressed bricks are composed of low sodium coconut coir and chips Each brick will expand to about 2.5 gallons when re-hydrated with water The coir brick provides excellent water retention and the chip brick improves aeration A custom mixture of the two creates an ideal growing medium for a specific growing environment Measures 15-4/5-inch length by 17-inch width by 9-1/3-inch height