his converter enables the use of normal DC adapters with DC plug/barrel 5.5 mm connector with Lenovo laptops which has female square plug. Please ensure the adapter you use has the matching and compatible power rating as that of your laptop. This pin is passive and only convert the interface not the power. One side is 5.5x2.1mm Female to Square Plug female plug, another side is square male plug for X1 Carbon Ultra book. Power converter Cable Adapter for Lenovo ThinkPad X1 Carbon 0B47046. Length around 5cm. 5.5x2.1mm Female to Square Plug. Female Interface Female End: DC 5.5x2.1mm. Male End: Square Port with Pin (Lenovo ThinkPad notebook dedicated power jack). Operating voltage allowed: 20V and 19V Load power is allowed: 90W, 65W, 45W. Function: The female end of this product can be plugged into a 5.5x2.1mm round hole mobile power charging bank or power adapter. DC Power Adapter 5.5 x 2.1mm Female to Square Plug Connector.