Abstract: A device for preventing refilling of a container such as a bottle is adapted to be slideably inserted into the neck of the container. The device includes a hollow, cylindrical body of plastic which includes an integrally molded shoulder which sealingly engages the neck. A valve assembly and a barrier for preventing access to the valve assembly are slideably received through an open end of the body and are retained therein by a resiliently flexible lip on the body. The valve assembly includes a valve seat provided with integrally molded spacers for supporting the barrier in spaced relationship to the valve. The barrier includes a plurality of screened members having interengaging, circumferential ribs which maintain the screens in spaced relationship to each other.