The present application relates to a mouthpiece (20) for an infant feeding vessel (10). The vessel (10) has a mounting collar (60) configured to be received between a receptacle (30) for holding fluid and a connector (40) for mounting the mouthpiece (20) to the receptacle (30) when assembled. The vessel (10) also has an air valve (70) in the mounting collar (60) to allow the flow of air into the receptacle (30) when the mouthpiece (20) is mounted to the receptacle (30). The air valve is biased towards an open condition in its unassembled state. At least part of the mounting collar (60) is resilient and is configured to be received between the receptacle (30) and the connector (40) when assembled. The at least part of the mounting collar (60) that is resilient is deformable to act on the air valve (70) to tend the air valve (70) towards a closed or further closed condition when the at least part of the mounting collar (60) that is resilient is compressed between the receptacle (30) and the connector (40)and in turn urged to deform in an inwardly radial direction of the mounting collar.
