A tip cap assembly adapted to close a fluid passageway of a distally projecting tip of an injection system, said tip cap assembly including an elastomeric inner cap having a frustoconical protrusion extending proximally and having a proximal face； a rigid outer cap which is securely disposed around said elastomeric inner cap； the proximal face of the frustoconical protrusion having a diameter at least greater than the diameter of the fluid passageway of the injection system.
