A RTK compatible GPS receiver, the so-called Rover, is required. E.g. the RGS 700 by Reichhardt.
An NTRIP modem, such as the RTK CLUE Modem is required, in order to receive RTK correction data.
A mobile communications antenna is needed to enable reception of RTK correction data.
A data SIM card is required, in order to receive RTK correction data via mobile communication networks.