Abstract: A fluid-holding container and a member for mounting the container to an object. The fluid-holding container is formed to have a concave bottom portion and sidewalls connected to the bottom portion. At the center of the bottom portion, a channel extends into the interior of the fluid-holding container. The channel is adapted to engage with a securing post of a mounting member. The mounting member includes a base portion that is attached to the object. The distance between the sidewalls and the center axis of the fluid-holding container is substantially equal to the distance between the center of the securing post and the base portion, thus assuring a secure attachment of the container to the mounting member. The present invention is suitable for use in mounting a water bottle to a bicycle.