BI WELDING CONCENTRIC REDUCER SCH40 ( SIZE 6" X 4", 6" X 3", 6" X 2" ) Concentric reducer is symmetrical, the center of two end are on the same line, while eccentric reducer is not symmetrical and usually used in the vertical pipeline. According to the manufacturer technique, it also divided into seamless reducer and welded reducer. Large diameter reducer often is welded in order to save cost.