Clear PTFE (Hydrophobic) Syringe Filters, 0.45 µm, 4 mm. PerkinElmer. Clear PTFE (Hydrophobic) Syringe Filters, 0.45 µm, 4 mm (200/Pack) have broad chemical compatibility and high pH resistance. These are versatile filters for use with aggressive organic solvent-based solutions and are especially ideal for HPLC sample preparation.