Small Mushroom Grow Bag for Spawn or Substrate Autoclavable Presealable 4" X 3" X 18" bags are perfect for running mushroom spawn Our bags are designed to withstand high temperatures that come with sterilization .05 Microporous filter patch keeps contaminates out and allows for gas exchange Presealable before sterilization and perfect for spawn production Much less bulky and awkward then traditional growing methods such as trays and tubs