Sterilized rye berry mushroom substrate bags with self healing injection port. Each bag weighs one pound and is equal to one quart in volume. Each bag has a five micron filter patch for proper gas exchange. These bags are hydrated and fully sterilized ready for you to use out of the box. Rye berry mushroom substrate is used to make your spawn. Once your spawn is fully colonized you will then mix it with a nutritious bulk mushroom substrate.