standard grade ptfe membrane Porex 0.2 Micron Standard-Grade PTFE Membrane Filter Standard-Grade PTFE Membrane Filter Cartridges 2.7" x 30" (Configurable) The Cary Company’s standard grade 2.7" x 30" filter cartridges with expanded PTFE membrane offer high purity filtration with micron ratings from .1 to .45 micron.