Filter membranes for microbiological analysis pore size 0.45 μm (HA), S-Pak, White with black grid surface; find Millipore-Z355534 MSDS, related peer-reviewed papers, technical documents, similar products & more at Sigma-Aldrich Filter type HA, 0.45 μm pore size, is designed to give complete retention and maximum recovery of total coliforms and fecal coliform bacteria.