The London Underground S7 and S8 Stock, commonly referred to as S Stock, is a type of passenger train running on the London Underground's subsurface lines since 2010. Manufactured by Bombardier Transportation's Derby Litchurch Lane Works, the S Stock was ordered to replace the A60, A62, C69, C77 and D78 stock on the Metropolitan, District, Hammersmith & City, and Circle lines, which all dated from the 1960s and 1970s. The order was for a total of 192 trains (1,403 cars), and consisted of two types, S7 Stock for the Circle, District and Hammersmith & City lines, and S8 Stock for the Metropolitan line, with differences in the arrangement of seating and number of cars. Both types have air-conditioning and low floors to ease accessibility for disabled people, and also have open gangways to all