The Sydney Trains K sets are a class of electric multiple units that currently operate on the Sydney Trains network. Built by A Goninan & Co, the K sets first entered service in 1981 operating under the State Rail Authority, and later CityRail. The carriages are of stainless steel, double deck construction and share much of their design with the older S sets. All of the 40 K sets originally built (160 carriages) remain in service and are currently the oldest in the Sydney Trains fleet.