These units are identical to the 170/5 except for having an additional vehicle, providing 74 more seats. All Turbostars are 23 – metre aluminium vehicles with “ribbon” glazing and 1300 mm wide swing/plug doors. Ride is excellent on the “series 3” bogies and the MTU 6R183TD13H engine produces little interior noise. Air conditioning is by AIT, the quietest and most reliable system in current UK use, and a PIS system is provided. Interiors are compliant to the RVAR except for minor details such as door close button heights, which are to an earlier specification. Large windows and powered interior doors also contribute to an excellent passenger environment. A BSI coupler provides full multiple working with Classes 150, 153, 155, 156, 158 and with minor modification Class 159, 165, 166, 168, 142, 143, 144. The UK’s most versatile unit.