The ER is an electric multiple unit developed from the MF diesel-mechanic units and also called IR4. Like the MF, it has inflatable rubber noses and cabs which can be folded away to form a gangway. Each unit contains four cars which rest on Jacobs bogies. Here only the first and last bogie is being powered with two 420 kW traction motors. While the MF has an interior designed for intercity services, the ER was developed for commuter service and has a modified interior. However, 24 sets were later modified for electrified intercity lines and received an interior similar to that of the MF.