This product is used to compensate for the longitudinal movement of steel-aluminum composite contact rail caused by thermal expansion and contraction due to temperature change. During the laying of the contact rail, an expansion joint device is installed every other anchor section to compensate the length change of the contact rail due to thermal expansion and contraction (compensation amount 200 mm) and to ensure that the current continues well. Length L according to the needs of the user, the recommened length L=l.4m (closedlength).