i tried 1/6 and it was to big. Futaba lists them as pan head truss screw part # 550360 in the manuel. I think they still come with every radio they sell. The screws go through the holes on the servo and then through a small brass sleave and then they can be screwed into a wood servo mount if the supplied plastic or nylon servo tray is too big to fit in the fusalage. The radio is a disscontinued Conquest PCM FP-T4NBP or just 4NBP on their website.