The bellows are essentially a tube. But not quite a tube, because when we say "tube", we normally think of something that has straight sides, that is, something that has the same diameter from one end to the other. The bellows are a tube that has a large diameter at some places and a small diameter in between. In other words, the bellows look like a tube made of corrugated metal (with the corrugations running around the tube, not end to end.) Return to XRS Intro