Whatman 6515-2502 Klari-Flex Polystyrene Funnel for Bottle-Top Filtration System, 0.22 Micron, 250mL Capacity (Pack of 12) Funnel; volume 250ml Pore size 0.22um; membrane PES; sterile Used to provide vacuum filtration of aqueous solutions such as cell culture media, biological fluids, and buffers Low-profile funnel and bottle filtration units are stable and tip resistant, minimizing the risk of spills and contamination