HO Diaphragm for 1 Bachmann Spectrum Heavyweight Cars. Black only. Includes car end doors, uses Kadee® #23 couplers. Close the gap with our innovative injection molded operating diaphragms. This easy to assemble kit turns a string of passenger cars into a train. Diaphragms stay connected in turn radii over 24 inches and have no minimum radius for smooth operation. Instructions are included with all kits.