A rubber band has three basic dimen

A rubber band has three basic dimensions: length, width, and thickness. (See picture.)

A rubber band's length is half its circumference. Its thickness is the distance from the inner circle to the outer circle, and its width is the distance from one edge to the other.

If one imagines a rubber band in manufacture, that is, a long tube of rubber on a mandrel, before it is sliced into rubber bands, the band's width is decided by how far apart the slices are cut.