The Trailer Plug Adapter is a 4 inch, 18AWG zip cord cable. It has a standard SAE two prong connector on one end and a 2.1mmID x 5.5mmOD barrel plug on the other end. This adapter cable can be used with the SUNLINQ Sunlinq 6.5, 12 and 25 watt folding solar panels line of products. The SAE plug connects directly to the solar panel and the barrel plug connects to various electronic devices and battery packs.