similarly each of the electronics packages coupled to the respective antenna 62 if separate remote control units 9 are provided or to the one remote control unit 9 if it is shared between the tools 11 13 15 prior to being included in the completion at the surface is separately programmed to respond to a specific signal the rfid tag comprises a miniature electronic circuit having a transceiver chip arranged to receive and store information and a small antenna within the hermetically sealed casing surrounding the tag once the borehole has been drilled and cased and the well is ready to be completed completion 4 and production string 3 is run downhole the sleeve 100 is run into the wellbore 1 in the open configuration such that the ports 26 are uncovered to allow fluid communication between the throughbore 40 and the annulus when required to operate a tool 11 13 15 and circulation is possible i e when the sleeve 100 is in the open configuration the pre programmed rfid tag is weighted if required and dropped or flushed into the well with the completion fluid after travelling through the throughbore 40 the selectively coded rfid tag reaches the remote control unit 9 the operator wishes to actuate and passes through the antenna 62 thereof which is of sufficient length to charge and read data from the tag the tag then transmits certain radio frequency signals enabling it to communicate with the antenna 62 this data is then processed by the electronics package as an example the rfid tag in the present embodiment has been programmed at.