Membrane filters for quantitative determination of microorganisms in QC analysis. Cellulose Nitrate (Cellulose Ester) and Cellulose Acetate filters are offered with or without a hydrophobic edge and/or grid, respectively. Sterile membranes are individually, packaged and are optionally available in pleated bands for use in filter dispensers such as the Microsart e.motion. High Flow membranes provide 30% higher flow rates than standard 0.45 µm filters.