Unless you have a tube-chassis-based ride, chances are your racecar started its life as a street machine with full emissions, convenience, and safety equipment. But as it begins to spend more of its life on the racetrack than the street, these pieces can outlive their usefulness and quickly find their way to the scrap pile in search of lower elapsed times and greater consisten- cy. Eventually ditching the OEM glass can become a tempting source of weight savings. Polycarbonate race windows are typically 50-75 percent lighter. But, to many, there are so many unknowns. Starting from the beginning, your OEM windows are made of strengthened safety glass. The windshield is made of laminated glass, which will not shatter when it is broken. A sheet of polyvinyl butyral is sandwiched between two pieces of glass. The layered effect withstands heavy impacts. The polyvinyl butyral acts like tape to hold the glass together and prevents people from being ejected through it in a crash. Conversely, the side and rear window are made of tempered glass, which is a process of strengthening via heating and cooling to put the outer surfaces into compression and the inner surfaces into tension. As the result, when it does break, it crumbles into rounded chunks rather than dangerous shards. Should you drive into a lake or roll over, shattering any of these windows with a metal punch can save your life.