Corning® 500 mL Bottle Top Vacuum Filter, 0.22 µm Pore 33.2cm² PES Membrane, Fits 45mm Diameter Necks, Sterile, 12/Case Fits plastic or glass media bottles with 45mm neck sizes. Polyethersulfone (PES) membranes provide the fastest flow rates, the lowest protein binding and low extractables and are best for filtering cell culture media.