Virtek PTFE comparison with competitive membranes. Virtek-PTFE-comparison-with-Pall-Versapor-R-Page. POREX Virtek® PTFE - The better alternative to other cast and expanded membranes. _______. See why POREX Virtek PTFE is a better option for your medical applications. If you need an alternative a discontinued or hard-to-source membrane, make