This is an adapter cable for use with Optimate Chargers. It connects to your charger and your vehicle’s cigarette lighter port, allowing you to charge your car battery without having to directly access it. This accessory has an industry standard 2-pole SAE tip going into an Auto/Bike plug (twist-off adapter). It fits Ø12mm BIKE/DIN or Ø21mm AUTO sockets. SKU: BC-OPT-CL2