Abstract: A device for fixing a metering member having a body, such as a pump, in the neck of a receptacle containing a substance to be dispensed, the body of the metering member having a smaller-diameter portion and a larger-diameter portion the maximum outside diameter of the body being smaller than the inside diameter of the neck the device being characterized in that the housing is formed in the neck of the receptacle, the housing being suitable for receiving a deformable member which, in the assembled state of the fixing device, is deformed and/or compressed in such a manner that it exerts a radial force on the neck and on the body, the force serving to fix the metering member in sealed manner in the neck of the receptacle, the deformable member being placed, prior to assembly, on the smaller-diameter portion and being deformed and/or compressed in the housing during assembly by the larger-diameter portion of the body of the metering member.