Abstract: A filter device removably retainable within a bottle for filtering fluid passing out of the bottle. The filter device is arranged to be insertable into any bottle. The filter device includes an insert component and a filter cartridge component. The insert includes an inlet and an outlet. It enables removable insertion into the bottle mouth with an interface sufficient to ensure that fluid cannot easily leak out around the sides of the device when in use. The filter cartridge is arranged to retain one or more filter media therein. It includes a fluid entry configured to direct fluid from within the bottle to come into contact with the filter media prior to its passage to the outlet. The filter device may be formed as a unitary structure or as a multi-component structure.