I just got a cross over box made out or aluminum today and the company who made it for me the welder and I were talking and I told him I liked his rear bumper on his old Ford pick up and he informed me and then showed me that it was not only a bumper but an air tank that holds enough air to fill his tires, and to carry an air impact to do any wheel changing. It looked like any normal drop bumper just sealed. I have never heard of this so I thought this was a great Idea! Anyone else ever hear of this?