The CORK head is the last piece to be attached above the screen, packer, and casing. The head contains the pressure sensors and data loggers. It also has valves and a data port that can be operated by a submersible or remotely operated vehicle (ROV). The CORK head will fit into the reentry cone on the seafloor to seal, or "cork," the borehole; the sensors will be down in the sealed hole beneath it.