Gold Label 713760 Custom 80/20 Mix is 80% Hydro Korrels and 20% Coco with added mycorrhizae. The sodium and chloride contents are extremely low for a coco substrate, ensuring a stable behavior throughout use. It is mixed with 80% Gold Label Special Mix Hydro Korrels, which is the substrate of choice for professional hydroponics growers around the world. Don't settle for inferior products containing heavy metals or other contaminates. Now you can grow like the pros with the substrate that was specially developed for serious gardeners growing heavy feeding plants.