Abstract: A container system for reagents and other substances used in a medical diagnostic apparatus. The container system includes a vial made of blow-molded plastic, which can withstand lyophilization. The bottom portion of the vial has an annular groove and is shaped as a truncated cone below the annular groove. An auxiliary member can be snap-connected to the vial at the annular groove so that the vial will stand upright on a flat surface and contains a central aperture through which the vial remains in contact with the flat surface. The container system also includes a stopper at the mouth of the vial and a snap-on plastic cover to secure the stopper. The cover has a tab which is kept at a raised position by a lifter protrusion which bears against the stopper. The cover has tearslots which are ripped when the tab is pulled. One of the tearslots is shorter than the other and keeps the tab from being entirely detached from the remainder of the cover when the tab is pulled.