Description from Amazon

Polycarbonate is a versatile, tough plastic used for a variety of applications, from bulletproof windows to compact disks (CDs). The main advantage of polycarbonate over other types of plastic is unbeatable strength combined with light weight. While acrylic is 17% stronger than glass, polycarbonate is nearly unbreakable. Bulletproof windows and enclosures as seen inside banks or at drive-throughs are often made of polycarbonate. Add to this the advantage that polycarbonate is just one-third the weight of acrylic, or one-sixth as heavy as glass.