. Pore Size: 20 µm. Compatibility: For use with 1mL SPE Tube. Pack of 216. . . Sigma-Aldrich 57244 Polyethylene (PE) Frit for 1mL SPE Tube, 20 µm Porosity, Pack of 216. Country of Origin : United States. Part Number : 1197T80EA. Pack of : 216.