The Microsoft Surface Book is a unique, ultra-thin laptop with a one-of-a-kind hinge that allows it to transform from a laptop into a clipboard or tablet. Its not just a productivity workhorse; the Surface Books multi-touch, PixelSense screen and Surface Pen make it well-suited for even the most intensely creative tasks. The Surface Books design is pure function. Much of the inventiveness in its form hinges quite literally on the new Dynamic Fulcrum Hinge, a flexible aluminum muscle with four rotational points to allow the laptops screen to easily, steadily bend all the way around to become a clipboard folio, or to detach completely to become a tablet. The screen detaches and securely reattaches with the push of a button, and is securely held in place by a Muscle Wire Lock made of nitinol, a metal that contracts when it comes into contact with an electrical charge. It includes a full-sized, back-lit keyboard; two USB ports; a DisplayPort; and an SD slot. The 13.5-inch screen, a 3:2 aspect ratio, was designed for maximum viewing angles, and is enabled for touch and pen.