If I remember correctly a crystal for the same brand AM will work in the same brand FM in most cases. I'm petty sure they did for the old Hitech ones, the futabas had different markings but I think they worked too. The things to watch out for are single or dual conversion and age of the system. Do a good range check to be sure all is right, in fact it's a good ideal to do a range check every time you go fly, an ounce of prevention.....