 The framework is built up from bent and extruded steel profiles, and consists of ring frames which are covered with corrugated sheet steel 1.5-2.5 mm thick.The automatic couplers and their shock absorbers are mounted on short spine beams at each end of the car.The doors and wire conduits are made of aluminum, which helped to keep the weight down and resulted in the cars being only slightly heavier than those of the ER1.