Patients will be randomised into one of two groups, with group A acting as the control group using the investigators' standard 3--point closed--face shell, and group B using the 3--point open--face shell (experimental group). Each procedure is discussed with the patient before commencement. Patients will be positioned into the optimal treatment position and the shell will be fabricated as per manufacturer instructions by pre-treatment radiographers. This is followed by the patient having a planning CT scan of their head while wearing their shell to allows radiographers and doctors to localise and plan the treatment. At the end of this appointment, the patient will be asked to complete the first of three questionnaires regarding their experience of wearing the shell. Radiographers will be asked to complete a questionnaire of their experience of using the shell, and complete timing data for the procedures.