The NS series 6400 is a four-axle diesel-electric locomotive for freight service and shunting with three-phase AC traction motors. The winner of the tender was MaK, with support from BBC for the traction electrics and electronics. It was based on the MaK DE 1002 and got the manufacturer's designation DE 6400 after its NS number. Each locomotive is being powered by an MTU V12 diesel with 1,180 kW or 1,600 hp. The AC traction allowed to combine a starting tractive effort of 305 kN with a top speed of 120 km/h. Groupe Eurotunnel ordered similar locomotives which are being designated DE 1004.

Between 1988 and 1994, 120 were built which received the numbers 6401 to 6520. Some were equipped with the necessary systems needed for operation in Germany and Belgium. Under Railion, some actually operated in Germany as class 264. From 2010, Groupe Eurotunnel bought five DE 6400 for tunnel rescue. Two were sold to DB Schenker Rail Polska and seven to Grenland Rail in Norway.