All the faders in the fader tray are identical so they can be swapped around if required. 

The master left, right, and mono faders are the same faders as the ones in the fader tray, but they have a lot longer wires attached to them.

The master faders could be used in the fader tray, however we wouldn't advise it.  The faders in the fader tray cannot be used for the masters and the wires are too short.

The two monitor faders are not moving faders.  These are soldered directly to the pcb underneath and cannot be swapped around