PTFE Membrane Filter, 55mm, Hydrophobic, 1.0 um, Used with EPA Method OTM 28 (Method 5 with 202), 50 per pack, SF17940. Regular Price $223.60 Price $179.50. Add to Cart. Add to Wish List. PTFE Hydrophobic Membrane Filters, 1.0 um, 8 inch x 10 inch, Nonsterile, 25 per pack, SPEC20105.