Pall® 4558 Acrodisc Syringe Filters with GHP Membrane, Pore Size 0.45 µm, Diameter 25 mm, Pack of 1000 . Filter Media: Glass Fiber / GH Polypro membrane (GHP, hydrophilic polypropylene) Housing: Polypropylene; Type: Syringe Filter; Use: Particulate Filter, Instrument Protection; Pore Size: 0.45 µm; Effective Filtration Area: 3.9 cm 2