Class 27 were the first of the Belgian Railways' large 1980s family of 144 electric locomotives. The family was made up of Classes 11 (12), 12 (12), 21 (60) and 27 (60). Classes 11, 12 and 21 were nearly twice as powerful as the preceding classes 22, 23 and 25. Class 27 was more than twice as powerful as these 1950s locomotives. The family was heavily influenced by the Class 202 locomotives built in the mid 1970s. They were very reliable because of the trial and error development of their predecessors. This family came into service with M4 and M5 coaching stock and the AM 80 and AM 86 series of EMUs. This generation was a major modernisation even if the older M2 coaching stock remained active for more than a decade. These four sister classes were visually identical except for a few minor details. Class 11's livery was specific to the Benelux service, which they operated for most of their service lives.