I bought this foot switch for my Fender Champion 40. It has two switches; one to switch between the clean and gain channel, and one to turn the effect on and off. Two lights show if the gain channel is selected and if the effect is engaged. With the foot switch the channel switch button on the amp itself does nothing.
It comes with an (instrument?) cable to connect the footswitch to the amp. Should you however lose or forget the cable, it also works with a normal guitar cable.
The unit is constructed from what looks to me as aluminium and plastic, and feels like it can take a beating. It however is pretty light and has no rubber feet, so it can move quite a bit if you put it on a smooth floor. I would recommend putting some rubber feet on it yourself.
For being a relatively simple piece of equipment, it seems a bit expensive to me, but I still wouldn't want to miss it, as it makes switching between gain and the clean channel possible without stopping playing.