The ThinkPad X1 series is a line of high-end ThinkPad laptop and tablet computers produced by Lenovo. It is a sub-series of the ThinkPad X series designed to be extra premium with material that make them lighter and portable, having been originally classed as Ultrabooks. While the ThinkPad T series is the flagship ThinkPad line, the ThinkPad X1 series's X1 Carbon specifically has been cited as a flagship model since its introduction in 2012.