Some solar panels come with wire connected to the wire box on the back of the panel. Attached to these wires are a male and female MC4 Connector.
These connectors join three solar panels wires together by simply plugging the three solar panels into a set of these connectors.
It will help make panel installation much easier and additional panels can be added in future by simply adding more of these connectors.
They are dust and waterproof.
The single wire connectors MC4 fit into these connectors as well.