Magnetic sensors are the main part of your machine and the pneumatic cylinder is getting orders from them to know when goes for " Reload " or " Dispense ".
Each machine has 2 magnetic sensors.
Stationery sensor
Moving sensor
You can see both sensors marked in the pictures.
Both sensors are the same type ( each machine needs only 2 ) 
Magnet sensor body dimensions: 26 mm x 12 mm
wire length: 40 inches