The Grow Block enhances all of the superb characteristics of the Grow Plug with its predetermined and buffered pH and EC values, to its self-regulating, air-to-water ratio. The Grow Block is extremely versatile and will perform in any application, and in all available cultivation methods. Direct replacement for Rockwool The Grow Block has several advantages over Rockwool including: higher yield, better quality, through improved root development and nutrient supply; lower costs, by eliminating the need for pots or sleeves; is eco-friendly and biodegradable. Sold in case lots of 90 blocks.