The ThinkPad X1 series is a line of high-end ThinkPad laptops and tablets produced by Lenovo. The current model list contains six lines of machines: * X1 Carbon - mainstream premium 14-inch model * X1 Yoga - the convertible 14-inch version * X1 Titanium Yoga - a convertible 13.5-inch version with titanium body * X1 Extreme - 15-inch advanced ultra-light premium laptop; the same model with a Quadro GPU known as ThinkPad P1 * X1 Nano - a 13.3-inch version - lightest thinkpad model * X1 Fold - the first foldable personal computer