When a projectile hits ballistic glass, the energy spreads sideways through each layer. The dispersal of the energy across a number of different pieces of plastic and glass allow the energy to be absorbed quickly. This process causes the projectile to slow so much that it no longer has the power to pierce or allow additional damage. Think of ballistic resistant glass as an "energy absorber" and you then will have a working understanding of how ballistic glass for sale on the market works.