We recommend using 0.4 μm pore polyester membrane inserts to culture airway epithelial cells at the ALI using PneumaCult-ALI Medium and PneumaCult-ALI-S Medium. Use Costar 6.5 mm Transwell, 0.4 µm Pore Polyester Membrane Inserts (Catalog #38024) for 24-well plates and Costar 12 mm Transwell, 0.4 µm Pore Polyester Membrane Inserts (Catalog #38023) for 12-well plates—both have been validated to support optimal ALI cultures using PneumaCult. See data showing superior ALI culture morphology and higher epithelial cell marker expression using these recommended Transwell inserts