Need help with motion selection

These two motion detectors are listed as compatible with the Elk wireless receiver:;ProdID=5884;ProdID=5895

I'm having a hard time figuring out the difference. Does anyone know the main difference?

Looks like one may be crystal osscilator for the transmitter vs non crysal I would say it depends on the receiver you plan on using it with.

I'm going to use them with the Elk receiver. They are both listed as compatible so they should both be crystal.