A variety of Polycarbonate produced by GE, it is one of the best and most common of the materials referred to as Bulletproof Glass (it's actually a kind of plastic, but is used in place of glass in many instances). One common place to find Lexan and other similar Polycarbonate varieties is in subway cars - Many subway windows are made of 1/4" tinted Lexan, to help prevent the window from shattering if anything happens to it. It has a density of 1.22 g/cc, making it less then half the weight of Aluminum. As a result, it is a very common lightweight armor for Battlebots. One notable Battlebot that uses Lexan is Killerhurtz, which is framed and armored almost entirely with Lexan.