Abstract: The disclosure provides improved vent filters useful in single-use in-line transfusion systems. In a first aspect, the disclosure provides filter comprising (i) a layer comprising a fluoropolymer membrane and (ii) a layer comprising at least two air-permeable thermoplastic polymeric layers, the air-permeable thermoplastic polymeric layers comprised of a first polymeric layer and a second polymeric layer, wherein the first polymeric layer is in bonded contact with the fluoropolymer membrane, possesses a melting point of about 95° C. to about 180° C., and wherein the second polymeric layer is in bonded contact with the first polymeric layer and has a melting point of about 220° C. to about 265° C. These filters exhibit excellent bonding strength between the various layers while preserving a considerable amount of the original fluoropolymer membrane air flux.