These cellulose filter discs are designed for regular mouth canning jars (70 mm diameter). Many mycologists prefer these cellulose discs over our regular synthetic discs because they are thick and rigid and pore size is guaranteed not to increase when autoclaved. They allow for gas exchange while providing 99.97% efficiency filtration down to 0.3 microns. Autoclavable. They are 100% reusable.
To use this filter, simply fit it snugly under the jar lid, or place it on top of the jar lid and secure it with the jar band.