HO Athearn F unit Connection Kit 3 pack (gray). For Athearn Blue Box locomotives. Comes with #6100 close coupling draft gear boxes and diaphragms for A-B-B or A-B-B-A lashups. Close the gap with our innovative injection molded operating diaphragms. This easy to assemble kit turns a diesel lashup into convincing scale power units. Diaphragms stay connected in turn radii over 24 inches and have no minimum radius for smooth operation. Use with Kadee® #5 or similar Couplers.