P3Solar (formerly Global Solar) 28001RC SAE Barrel Plug Adapter - SAE to 2.1mm ID x 5.5mm OD Barrel AdapterSAE to 2.1mm BARREL PLUG A 4 inch, 18 AWG 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. The SAE plug connects directly to the solar charger and the barrel plug connects to various electronic devices and battery packs.