BRF bags are a fun and economical way to grow on brown rice four and vermiculite mushroom substrate. Simply inoculate the bag with 2-4 cc of your gourmet mushroom spore solution, or 5-8 cc of liquid culture, and let it grow. These bags contain 8 ounces of brown rice flower and vermiculite mushroom substrate, which is much more than others sellers use in their half pint jars. Simply inoculate the bag with 2-4 cc of your gourmet mushroom spore solution, or 5-8 cc of liquid culture, and let it grow. Brown Rice Flour mushroom substrate mix is 100% sterilized and ready-to-use at your front door. The substrate has a light consistency after it is broken up, so that it is very easy for mycelium to colonize. This mushroom substrate is enhanced with all necessary nutrients and moisture needed for healthy, large fruits. The substrate contains vermiculite, brown rice flour, multigrain flour and gypsum.