Container assemblies for accommodating pharmaceutical compositions are provided. The container assembly includes a container and a plunger. The container has a hollow cylindrical body with an open end and a closed end, which is closed by a bottom portion. The hollow cylindrical body has a length (L), an outer diameter (DO), and an inner diameter with a length to outer diameter ratio between 3:1 and 15:1. The hollow cylindrical body and the bottom portion are formed integrally and of the same material, which is a glass or polymer material. The container has an inner surface with an average Zn-leachability of 0.00085 μg/cm2 or less. The plunger is inside the hollow cylindrical body at the open end, is pierceable by a cannula, and is slidable relative to the hollow cylindrical body from the open end towards the closed end.