Corning® Syringe Filters, Sterile, Diam. 28 mm, Pore Size 0.2 mm, CLS431218, Corning, Inc. (CAT#: STEM-L-4269-Y) Syringe Filter, MCE, 0.22μm, 33mm, STE-Mart (CAT#: STEM-FC-0465-LC) Whatman ® UNIFLO ® 13 Syringe Filters, PVDF Membrane, Pore Size 0.22 μm, Pack of 500 ea, Whatman International Ltd. (CAT#: STEM-L-4913-LC) Millex Syringe Filter