Type B filter has high gas exchange characteristics. With 90% pore coverage, the pore sizes are larger than the A filter, at 5 microns. Due to these characteristics, B-filtered bags can be sealed before autoclaving. For most other bags, either the filters allow competing fungi to enter, or too-small pores will pop during autoclaving.

T filter has 0.2-micron pores. They are 90% efficient and are designed for spawn production.

Type A filter is designed for shiitake cultivation. It has a nominal 0.5-micron pore size, meaning 80% efficiency at approximately 0.5 microns. This filter was also designed to have a surface area of 50% for breathability. This allows shiitake mycelium to grow in a higher CO2 environment.