PTFE for PM2.5 Particle Monitoring, PTFE, hydrophobic, 2.0 µm, 47 mm, white, plain, polypropylene ring, sequential serial number. The PTFE Membrane for PM2.5 Particle Monitoring is a filter disc used in conjunction with PM2.5 Environmental Monitoring equipment., PTFE membrane, hydrophobic, pore size 2.0 μm, white filter, plain filter.