Corning 500mL Vacuum Filter/Storage Bottle System, 0.22Âµm Pore 33.2cmÂ² PES Membrane, Sterile, 12/Case â€¢ Polyethersulfone (PES) membranes provide the fastest flow rates, the lowest protein binding and low extractables and are best for filtering cell culture media. â€¢ 250mL receiver bottles feature easy grip sides for improved handling. â€¢ Additional storage bottles can be purchased to increase capacity. â€¢ Bottle caps are supplied sterile and individually packaged. â€¢ Angled hose connector simplifies vacuum line attachment. â€¢ Individually packaged, sterile and certified nonpyrogenic. â€¢ Each system has the membrane material and pore size printed on the unit and is color-coded by membrane type for easy product identification. â€¢ Expiration date appears on the filter funnel and shipping boxes. â€¢ Expiration date of the membrane is three years from the time the product is manufactured.