When a window is created, it is run through the small and large missile test. A small missile test is when a small object is propelled at the window at high speed to see if it breaks. The large missile test is the same but with a larger object. Windows that only pass the small missile test can only be used in building that that surpass 30 feet. Windows that pass the large missile test are used as windows under 30 feet. Windows are tested this way because windows that are above 30 feet are less likely to be hit by large objects. As larger objects are heavier, they tend to stay closer to the ground. Although large missile windows are primarily used for under 30 feet buildings, it can be used higher than 30 feet as well.