The Sydney Trains M sets, also referred to as the Millennium trains are a class of electric multiple unit operated by Sydney Trains in Sydney, New South Wales, Australia. The fourth generation trains entered service from 1 July 2002 after short delays due to electrical defects. The trains can operate over the entire suburban network, but currently only operate on T2 Inner West & Leppington, T3 Bankstown, T5 Cumberland, T7 Olympic Park and T8 Airport & South lines.The M sets replaced the 1960s Tulloch trailers and provided extra capacity on the CityRail network.