Teflo Air Sampling PTFE Membrane 2um pore size. 41mm diameter. PMP support ring for PM10 and PM2.5 dichotomous and other air sampling techniques. 25um thickness. 53Lpm/cm2 at 0.7bar air flow rate. 99.99% typical rosol retention following ASTM D2986-71 0.3um (DOP) at 32Lpm/100cm2 filter media.