[AllenGregoryIV]

Compatible pneumatic pistons have a magnet that rides on the piston. When the magnet is next to the sensor it connect the two wires (I believe it is normally open but I might be wrong). By placing two of them on a compatible pneumatic cylinder (I think the FIRST ones that are compatible have an M in the part number) you can detect if the piston is extended or retracted.

And Yes I believe that is all the parts. The metal strap wraps around the cylinder and holds the sensor in place.