Casing is the product most people would choose to use as the top layer of their mono tubs after your colonized grain spawn and compost soil have been mixed together and have further colonized. Then adding a casing layer to the top of your tubs helps regulate the PH of your product and also adds nutrients and moisture for more flush harvests from the same tub. These bags come the same way the Compost soil does, moist, sterilized and ready to use whenever you decide to open it. It stays good on a shelf for a long time as well, since it is also sterilized 3 times and delivered in airtight bags. These bags were created through many years of trial and testing with multiple farms, they are mineral and PH balanced by scientists who have degrees in Soil Science, Agriculture and Mycology.