Microsoft started its own line of 2-in-1s with the introduction of the Surface Pro series, the first of which was released in February 2013.[30] It had a 10.6-inch (27 cm) display, Intel Core i5 CPU, and included the Pro Pen stylus and a detachable keyboard that doubled as a protective screen cover. In 2015 Microsoft introduced the Surface Book series, which, similar to the Surface Pro series, features a detachable keyboard cover and Surface Pen stylus.