CTEK Cig-Plug enables charging the battery through the cigarette outlet. It eliminates any hassle, simply charge from within the car, suits perfect for CTEK battery chargers with Comfort Connect, UC 800, us 800, MULTI US 3300, MULTI US 4. 3, 4. 3 Test & charge, 4. 3 Polar, MXS 5. 0, CT5 Time To Go, Multi US 7002. Note: The socket in the vehicle must be live when the ignition is in the “off” position to charge your battery using this accessory. CTEK Cig-Plug fits both 12 millimeter and 21 millimeter outlets and has a maze-like strain relief for the users safety.