2 layer board of 2.71x2.11 inches (68.73x53.47 mm). For when you need to switch the positive side of your load (common cathode) instead of the negative side (common anode). Most FET shields use N-Channel MOSFETs which switch the ground connection, assuming the positive connection is always connected to power. This shield uses P-Channel MOSFETs which switch the positive, so it’ll work with loads that have a common ground (like this aquarium light ) The input is designed to take a PCB mounted Anderson PowerPole connector, but you can solder wires directly to it just as easily. Components are as labeled on the board: FQP27P06 BSS138 10k 1206 SMT resistor (take your pick) 1N4148 or any other rectifying diode. It’s just there to prevent the Arduino from trying to feed power to a potentially large load hanging off the MOSFETs.