PTFE Membrane, WTP Range, 0.2 µm pore size, 47 mm circle (100 pcs) 28420777. PTFE Membrane, WTP Range, 0.5 µm pore size, 47 mm circle (100 pcs) 28420778. PTFE Membrane, WTP Range, 1 µm pore size, 25 mm circle (100 pcs) 28420780. PTFE Membrane, WTP Range, 1 µm pore size, 47 mm circle (100 pcs) Overview. Overview.