The present invention relates to a medical device for administering a medicinal product to a patient comprising at least air component (2 8 10 12 14 15 16 17 18 20 22 24 26 28) comprising a material having an additive embedded therein wherein the additive is adapted to provide a visually perceptible signal when exposed to electromagnetic radiation. The invention is particularly intended for drug delivery devices such as e.g. of pen-type injectors. With the visually perceptible signal embedded in the at least one component visually controlled assembly of such devices can be improved. Additionally the invention provides an effective means antagonize counterfeiting of drugs and of medical devices.
