Lo band includes channels 11-35, Hi band includes channels 36-60.

Modern Futaba receivers are tuned for Hi or Lo bands, and you can change channels within the Hi or Lo areas without problems.

Older receivers were tuned to the exact channel they had when new, and would keep tuning to about 6 channels or so on either side of the original channel. Any more, and retuning was strongly recommended. If you want to use a Hi channel in a Lo receiver, or vice-versa, the receiver should be retuned to the new band, otherwise range problems may result.