The plastic bodies join together in a variety of ways for polarization purposes. Solder your wires into the big 1/8" ID hole in the silver-plated contact. Reasons to use Powerpole Connectors: (1) Resistance of the mated connectors is very low (this prevents loss of power). (2) Large high 14-12 ga. capacity wires fit into the holes in the pins. These are compatable with Sermos Connectors