This is a heavy duty 2S hard case lithium polymer battery charge lead lead from ProTek R/C. This charge lead has 4mm banana plugs on both ends, as well as a 2mm banana plug on the battery end for balancing. This charge lead is specifically designed to connect a 2S lipo hard pack to ProTek R/C chargers, but will also work with any charger that uses 4mm bullet connectors for output, and an XH balance adapter port.