This specification covers dry–cast segmental retaining wall units of concrete, machine–made from hydraulic cement, water, and suitable mineral aggregates with or without the inclusion of other materials. The units are intended for use in the construction of mortarless segmental retaining walls. The material composition of retaining wall units consists of cementitious materials like portland cement and its modified form, limestone, hydraulic cement, blended hydraulic cement, pozzolans, blast furnace slag cement, aggregates, and other constituents which include air-entraining agents, coloring pigments, integral water repellents, and finely ground silica. All units shall be sound and free of cracks or other defects that interfere with the proper placement of the unit or significantly impair the strength or permanence of the construction.