This figure shows the cross section of one of the bellows sections of tubing. These are not bellows in the sense of fireplace bellows that you use to blow air onto a fire. Instead, they're metal tubes. They're called "bellows" because sections of them are corrugated in a way that reminds people of the corrugated sides of fireplace bellows.
If this picture were a cross section of a plain metal tube, it would just be 2 straight, parallel lines. In fact, the 2 ends of the diagram are straight, parallel lines. In between the ends, the lines become zig-zag, representing the corrugated sides of the bellows. Return to XRS Intro