Protective Armor Systems bulletproof glass (Western Massachusetts)

Here are some other structural materials. Here's bulletproof glass — four layers, three of which are glass adhesively bonded in between. It's very important how you put the adhesive in. You don't want bubbles, because you're supposed to be transparent — you don't want to be looking through bubbles. One layer is polycarbonate, the toughest plastic known. Polycarbonate by itself used to be bulletproof glass, but we have better bullets now, so it's basically a composite. This is made by a company called PAS, Protective Armor Systems, out in western Massachusetts. They make a five-and-a-quarter-inch version with about six layers, which goes on the windows of the president's car. The thicker one will stop an RPG — a rocket-propelled grenade. That's like the shaped charges they used in Iraq.