When the line first opened it was served by a fleet of 8-car 1967 tube stock trains. Each is made up of two four-car units. Later on, a number of cars of 1972 Mark I tube stock were adapted to work with the 1967 stock. This meant that there were finally 43 trains, each of which was made up of two four-car units. The 1967 tube stock was replaced by 2009 tube stock between 2009 and 2011 (see below).