The armored glass of the Cadillac was almost one centimeter thick, plus around 1,360 kilograms of armored steel. Strong spring balances helped to operate the heavy side windows - they could be raised 2.5 centimeters and then opened a hole. Through this hole, Al Capone's men could shoot outside with their Tommy Guns if necessary. The rear window could be folded down - also to have a clear line of fire on pursuers.