The Professor Motor solid-state electronic controller design is a major breakthrough in controller technology that has revolutionized the slot car driving experience. Its big advantage over earlier resistor controller designs is that you can use just one controller to drive a wide variety of cars with different motor and nagnet installations that would have required several resistor controllers with different resistance values. If you drive a wide variety of cars this makes the PM controllers worth the price because now one controller can do it all saving you money and space in your race case that can be used to carry more cars and parts. PM controllers are made with top-quality materials and components for durability and reliability. They are repairable in the event of damage or component failure and a range of available upgrade kits makes it easy to add additional features to your controllers.