A device that has a device body defining an opening at one end thereof, a storage chamber within the device body for storing multiple doses of a substance therein, and a sliding stopper, sealing engageable with the device body, through which the chamber is filled. The stopper has a body and a flexible portion, which may be in the form of a plurality of flexible members, extending therefrom. The flexible portion or members are movable between first and second positions. In the first position, during filling, the portion or members are substantially laterally extending from the stopper body and engaging the opening of the device body. Accordingly, the axial position of the stopper with respect to the device body is secured during filling of the chamber therethrough. In the second position, after filling, the portion or members are substantially axially-extending from the stopper body and disengaged from the rim or opening of the device body. Accordingly, the stopper is axially slideable through the body.
