To replace the Class 80 diesel-electric multiple units of the seventies, Northern Ireland Railways ordered 23 three-car diesel-mechanical multiple units from CAF in Spain in 2002. They come from the family which CAF calls the CxK and were delivered to the Irish Railways back in 2002 as Class 29000. At a total cost of £80 million, this was the largest order NIR had ever placed.
The trains, known only as C3K for short, have a six-cylinder from MAN with 460 hp per car, which drives both axles of a bogie. The first six sets are equipped with the Irish train protection system CAWS in order to be able to serve international routes. They were supplemented from 2011 by the Class 4000 from the same family by CAF and modernized from 2018.