Following a change of regulation in 2015, all Radio Control handsets and receivers now operate on the "crystal free" 2.4ghz wave band.
This has two significant advantages compared to the older 27 / 40 and 49Mhz wave bands sold in the past - no crystals and rarely any interference.
Each radio handset is locked (a process called "Binding") to it's own receiver. You can re-bind the handset to a new receiver, but it will never "accidentally" connect to one it hasn't been bound to. The result is that you can switch on as many radios as you like, and they will only control the model they're bound with. No more checking frequencies and no need to swap crystals around.
The other advantage is that, given 2.4Ghz operates on a much narrower physical radio wave, the handset aerials are only a few inches long, as are the receivers - eliminating the long and easily damaged telescopic aerials previously used.