To elaborate, not only do you have to get the same brand but you also have to make sure it is either single or dual conversion to match your receiver. The crystal has to match your reciever, not your transmitter.
IE... you have a Futaba transmitter which will work superbly with a Hitec Supreme II receiver for example so in this case you will use a Hitec Dual Conversion crystal (even though your radio is Futaba) on the channel your Futaba transmitter is on.