Filter bag. The bag has several microporous filters incorporated into it so gas can pass in and out but moisture stays in and contaminants are kept out. This is important as during mycelium growth phase, a lot of CO2 is given off and needs venting, but the medium must not dry out. In short, the bag creates and maintains the perfect environment for shroom growth. These bags are autoclavable.
Suitable for use with 1200ml kits