An embodiment directed towards a system for ambulatory drug infusion over an extended time period from a flexible container is disclosed, and in which the system comprises a filling apparatus with a hollow support structure defining a container compartment, the container compartment being adapted to receive, fully or in part, the flexible container, and the support structure being adapted to limit the expansion of the flexible container by contacting the flexible container upon being filled, thus defining a maximum filling volume of the flexible container. In other embodiments, a container assembly is disclosed that comprises a flexible container and a support structure as well as use of a flexible container in or in combination with a system according to the invention or a container assembly according to the invention.
