The 2 digit numbered Futaba servos (S48, S28 etc.) are the older "G" style connectors. The 3 digit (S148) are "J" style connectors. Make sure your TX & RX are narrow band. Your RX is narrow band if it is a 3 digit model # (R114, R117, R118), if it is a 2 digit it is not narrow band and not approved for use. Your TX should have a gold sticker on the back with a date on it. Is you system AM or FM? These are very reliable units.