 So we were using rocket launchers, an RPG-7, and we wanted to study the effects of... It's called backblast. It's all of the propulsion coming out of the rear of the Venturi. It's where all the gases go that move the rocket in the other direction. And it's long talked about through militaries around the world that you always clear your backblast because it'll kill somebody. And so what we do is we take...