A fastener device for fastening a dispenser member on a neck of a reservoir, the device including a fastener ring. The fastener ring having reception mechanism for receiving, in stationary manner, the dispenser member; an annular plate for exerting axial pressure on the neck; and a fastener skirt that extends downwards from the plate, the skirt including a fastener mechanism for fastening around the neck. The ring is made of two different plastics materials, a substantially-hard first material and a flexible second material that is more flexible than the first material. The device also includes a hoop that, in the final assembled position, extends around the skirt of the ring with radial clamping. The flexible second material comes into contact with the hoop.