Crowtail- MOSFET enables you to control higher voltage projects, say 50VDC, with low voltage, say 5V, on the micro controller. MOSFET is also a kind of switch. There are two screw terminals on the board. One for the 5input power source and the other for the device you want to control. Crowtail- MOSFET will pass the power from one end to another when closed. But if an outer power source is absent, your device can still draw power from the microcontroller via the Crowtail interface. There is a mini fan that our customers can choose from, you can do some interesting projects with the mini fan.