The U sets were a class of electric multiple unit (EMU) operated by the New South Wales Government Railways and its successors between September 1958 and November 1996.

[1] The New South Wales Government Railways began planning the electrification of the Main Western line over the Blue Mountains from 1949, and with that plan in full swing by the early 1950s, called tenders for 80 cars (40 motor, 20 trailer and 20 first with buffet trailer), with the contract was awarded to Commonwealth Engineering, Granville, in 1954.

However, before construction began the order was amended with the 20 planned first with buffet cars built as full first class seating cars, after a review of the New South Wales Government Railways conducted by American firm Ebasco Services Incorporated in the mid-1950s recommended the change.

[1] The U sets were a bit different compared to the suburban single decked trains that were delivered at the same time.

The U sets initially operated on the Main Western line as far as Bowenfels which was the limit of the electrified system at the time.

[3] Most of the cars allocated to the Hunter Valley Railway Trust were scrapped in 2013, excepting CF 5001.