Model 2517-D1 was designed to fit Demco style Cast trailer couplers. This style trailer coupler is usually found on heavy duty enclosed car trailers such as those used in show car transportation applications, Demco style trailer couplers will be found on enclosed car trailers, but in some cases trailer manufacturers offer Demco couplers on non-commercial trailers as an upgrade. If you have a Stamped Demco Coupler Please see Model 2517-D .