A Radio Frequency Identification (RFID) tag, 106, is mounted on a base, 102, made of electrically conductive material (e.g. metal). The RFID tag comprises an integrated circuit (IC, chip), 108, and an antenna (aerial). The RFID is coupled to a first side of the mounting base and sealed with a cover, 202, made of RF transparent material. The cover is moulded over the RFID tag such that the cover and mounting base encapsulate the tag. The RF transparent material is injection moulded and delivered in a molten state. The material is allowed to cool as it flows towards the IC such that its temperature does not exceed the maximum tolerable temperature of the chip. The mounting base may have tags or tabs extending from each end, 104, to facilitate mounting of the device. The RF transparent material may be polyphenylsulfone. The RFID tag assembly may be mounted onto the metal body of a surgical instrument.
