The PTFE Teflon syringe filter membranes are backed with an inert polypropylene membrane for support.
All the others syringe filters including Nylon, Regenerated Cellulose, Cellulose Acetate, PVDF etal do not require additional support and therefore have no additional membranes.
Click HERE for ordering information and pictures of AQ brand syringe filters
Attachment
MicroSolv Filters Equivalency Study pdf Download File